Okay, so I've had a skim over the topic and will address things that I feel need to be addressed, including mentioning things that I feel should be kept under consideration.
If I earlier mentioned something "will not happen" and I don't mention it here again, assume it's still a "will not happen". If I haven't responded to something at all, including here, feel free to bring it up again - it is probably going to end up overlooked completely otherwise (and it's very likely not intentional that they've been overlooked so far; it's easy to overlook some things when trying to put together a list of points to respond to then actually respond to them).
Some points are mentioned here as needing further discussion. Now is not the time to discuss them further - for now, please focus on if there's any points brought up that I've overlooked here, or any outright new suggestions.
General
Overall approach
It seems that even without worrying about whether people are willing to accept a total do-over, the most practical approach would be revisions to the existing menu - some of them relatively heavy, but still ultimately revisions rather than a whole new menu. So at this point, let's proceed under the assumption that we're keeping the existing menu as a base, but are open to strong changes.
Multiple menu styles
After further thought, it simply feels like there's too much room for disaster if we try to keep multiple menu styles in place. This means no "Legacy Mode" in particular.
Menu sizing
There are two different types of suggestions that have been made with regards to altering the menu screen sizes.
The first is to have - it was never really clear to me whether this was "as an additional option" or "make it the standard" - a high-resolution menu. This is not going to happen. The menu's resolution is already equivalent to in-game high-res, I see nothing to be gained from thus dividing the menu into "high res" and "higher res". If anything, there would be a stronger argument to have a low-res mode in line with the game; but that feels utterly pointless too and will not happen.
The other one is to keep the same resolution, but adjust the sizing. The proposals were 800x400 or 711x400, both of which keep the existing height but adjust to widescreen proportions. I am willing to do a size change if it is specifically to a widescreen resolution. In such a case, I would like to aim for 16:9 specifically, though this need not be specifically 711x400 - eg 854x480 could be considered. The crucial details are it shouldn't be too different (aside from proportional adjustments to the width) from the current one - so eg. 1280x720 is out of the question.
One other case in which I'd be willing to adjust the size is adjusting it, either vertically-only or proportionally, if the font height is increased. Whether or not the widescreen thing happens, I will insist that it remain possible to fit 25 lines of text on-screen (for the sake of existing preview / postview texts).
Note that the menu would still behave like it does now in most regards - you could resize the window to a different proportion (menu zooms as much as possible while still remaining 100% visible, with black bars filling in the remainder) or a different size (zoomed in / out), the "size" here is really just the internal size used for rendering it.
tl;dr: Resolution changes ruled out, size changes okay if specifically moving to widescreen and/or to adjust for new font size, must be not too far from widescreen equivalent of current size but doesn't have to be exactly that, must fit at least same number of lines of text as current size (taking into account, if applicable, new font sizing).
Resampling algorithm
It was proposed that the high-res-mode resampler be used for the smooth resampling in the menus. Unfortunately there are multiple reasons this cannot be done. The biggest concerns are firstly, that the high-res-mode resampler is not fast enough to be used for live rendering (as it was written with the intent it would be used only at load-time, thus, speed is not a critical concern); and secondly, that it is specifically written to handle exactly a 2x zoom. You could achieve powers of 2 by applying it repeatedly (though I don't know how well it would work after multiple iterations), but even other integer values, let alone non-integer zooms, would require significant adjustments to the formula.
tl;dr: Impractical to use high-res resampler for smoothing, so it won't happen.
Add / remove some menu screens
Removing the Talisman screen has been proposed, in favor of the talisman list being integrated into the level select menu - with a full list for a given pack (and perhaps for a given rank, too) being visible when the pack, rather than a level in it, is selected.
It has also been proposed that features like mass replay test, cleanse levels, etc be moved into a dedicated "Creator Tools" submenu. This menu may end up being a bit on the empty side at first, but once it exists it may also be that we find more useful stuff to add to it.
Cursor
It has been brought up that a cursor graphic needs to be decided on (though just using the Windows default is not out of the question). Using the high-res in-game cursor has been proposed, though some people prefer the idea of using the low-res one scaled up. I'm open to either, as well as to completely custom ones.
Background
Proposals to use a different or less-edited background image have been brought up. Happy to replace if there's consensus over a new graphic to use.
Alteration to font height / color
Open to this if it's generally supported, but someone else will need to produce (or rip from Amiga, if applicable) the new font graphic. The menu screen size will need to be adjusted if this changes, to ensure that 25 lines of text can still fit on-screen. One target here could be 640x480 or 854x480 (4:3 or 16:9 respectively) with an extra 3 pixels of height added to the font.
Regarding the color, I'd need to see strong support before implementing any "multiple colors are used" setup like Amiga or SuperLemmini have, but I'm not outright opposed to it. I'm quite happy to go ahead with a "keep a one-global-color setup but change what color it is" approach, and I like Dullstar's (IIRC) mockup from earlier in the topic as a potential color to use. I will note that the suggestion of tweaking the font color seems to have support even among some people who are strongly against most changes to the menu, so this particular change could be considered all but guaranteed to be happening.
Main Menu
Logo sizing
This was originally proposed as allowing one of several sizes, or even just requiring a new specific size. There is basically no reason this can't become "allow any arbitrary size, up to a certain cap", with smaller logos being centered on the available area - so this is likely what will happen here.
One row of cards
If they fit - which may be more so with a move to widescreen - sure. Following on from some of the other proposals, it appears we'd need 6 cards: Play, Level Select, Settings, Rank, Creator's Tools, Quit. Not sure if 6 would fit without adjusting their size, which would be preferable to avoid for the sake of existing custom ones - though this could also depend on what the size actually ends up being.
Clicked graphics for cards
Open to this. If we're considering it, we may want to also consider decoupling the parts of the card graphics a bit more (seperate graphic files for the lemmings holding the cards, the cards themself, and the text / graphic on the cards) - this might make customization tidier too. The downside is that even implementing this at all will likely be a backwards-compatibility break, although at least one that only affects cosmetic aspects of packs.
Animated cards
If there's a lot of demand for this from people who are actually intending to make animated cards themself (not just those who think "it'd be cool to see this in a pack") I could look at it. Most likely though, I wouldn't hold my breath on this one - it's a lot of work for not much gain. If the graphics of the cards are decoupled as per above, it could be considered whether only some parts can be animated.
Load replay directly from menu
I like the idea at the most basic level, but I question whether it's the most effective use of menu screen space. With that being said, I'm not sure where else to put it. It could perhaps be accessed by right-clicking an existing panel, though ideally I'd like to move away from "hidden" menu features like that.
Level Select
Additional info about level
I absolutely agree on this. At the very least it should show the level's stats, skillset and talismans. The "what layout?" is a finer point to discuss later.
Display player's records
Yes, I'm in favor of this idea. I would prefer that it be on a secondary tab, away from the main level info.
Search by level name
I understand this was a feature Nepster promised a while ago, but didn't get around to implementing before he left the forums. It's something that should happen - though I'm not promising it will happen as part of these revisions (as it is, really, a major new feature on the inside, even if it seems quite minor on the surface).
Find replays for level
Or some variation, like "show all replays for this level" in the level select menu. Nice idea, implementation could be tricky though - and could have a HUGE performance impact if the player's replay folder has a lot of replays. Unlike Lix, NL does not have particularly strong links between level files and replay files - it has mechanisms to match them up, but these are more designed for "when presented with a level and a replay, check whether or not they match up" rather than "when presented with one, find the matching other".
Preview / Postview
Additional level info
It has been proposed that more info about the level could be displayed, perhaps in the form of a "mock skill panel" showing the release rate (including whether it's locked or not) and skillset. This would almost certainly not include the always-present-never-changing buttons like pause, nuke, etc, nor the info above the main panel.
Talisman info
There seems to be agreement that something needs to change; there isn't so much agreement about what it should change to. Proposals so far include "don't show it at all" and "show icons to indicate that talismans exist / how many / what color, but nothing more". A more complex proposal, tying into the above, is to have clickable talisman icons that adjust the skill display / etc to reflect the talisman requirements.
"Continue", "Exit" etc options
In line with the general mouse-friendliness goal, the "Press ____ button to _____" texts would be replaced with simple "Play", "Exit", etc labels (exact wording to be decided later) that are clickable.