I agree with Icho, but I'd add that the level intro texts are also extremely important, given the pack's tutorial purpose. In my opinion, the intros in the old pack are much too long and might be off-putting to new players. Either one person should be in charge of writing all the level intros for the pack, or at least, one person should have general permission to edit all the level intros to bring them up to acceptable standards. I'm happy to volunteer for this, and I can also make some levels. I can't set aside very much time for the project right now, but I could at least try to do one per week.
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Regarding the content, I've had a quick play through the "Skills" rank of the old pack -- I chose "Skills" because the idea of making the pack accessible to players who've never seen Lemmings before means that Skills has to come first.
I don't think we should keep the idea of always having one level with just the skill being introduced, then one level combining it with other skills. Firstly, that means the climber, floater, glider and swimmer levels are all going to be essentially the same: "click on
n lemmings". Secondly, it means the walker level can only show the turning walker, with the walker's function of stopping other skills being relegated to post-level text. Thirdly, it means that the rank needs no fewer than 36 levels (38 with shimmiers). An intro pack should teach the player what they need to know before playing other packs, certainly. But it should also teach them that
the game is fun and interesting. The sooner we can get the player off completely trivial levels and onto real puzzles, the better.
It will be necessary to decide what order we're going to introduce the skills in, since each skill can only be combined with others that have been previously introduced. Some orderings are obvious: the glider, being a more complex version of the floater, must come later (and then its intro text can explicitly compare it to the floater). The blocker should come before the exploder and walker, so that we can show them being applied to blockers.
Possibly, the very first level should be winnable by doing nothing; then its intro text can talk about the basic rules of the game and what the numbers above the skillbar mean. In the old pack, this is explained in a
post-level text; but it's pretty infuriating to be told "here's something you should have noticed, but probably didn't".
Some hotkeys should also be introduced either before or alongside skills, particularly fast-forward and 10-second skip
And the intro texts should mention the skill shadows (is there an official term for these?)
Regarding Skills 8: as well as being too hard, it's backrouted (at least, I didn't need all the skills given) and uses the Purple tileset with its traps that are invisible unless you know what to look for. I don't like this level at all.
Skills 20 on the other hand I have no problem with, it's a good level for the "exam puzzles" rank.