You confuse complexity and difficulty
We can argue definitions of what counts as "complex" or "difficult" all day. The bottom line we keep coming back to, because you keep emphasizing it as your goal, is "friendliness towards new players".
Confronting a new player with NepsterLems would be just as pointless as overwhelming him with the feature diversity of Paralems: Frustration would kick in way too soon, because it takes a while to figure out all the things you can do even with just the classic skills. So a new player should be pointed towards either original Lemmings, or something like SubLems or CasuaLemmings.
A more seasoned player (let's define this as someone who has played through original Lemmings and ONML) will seek for new challenges in one way or another. For some players, this will consist of taking only things they already know, but taking them to great extremes, like Nepster Lems or Lemmings Migration. For others, it will mean getting into contact with new skills, like swimmers, fencers, and disarmers, or objects, like splitters, teleporters, and possibly also radiation and slowfreeze. Indeed, for someone who has played through original Lemmings and original ONML, the concept of radiation shouldn't be that foreign, apart from the fact that the countdown takes longer. And then it just makes sense for the other lethal skill (the stoner) to have a similar thing (slowfreeze).
Hence, there is no point in trying to "protect" players from over-complexity, or from the challenge of memorising lots of things. Because players will seek these challenges for themselves, and they will also pick and choose which type of challenge they prefer. Just look at all the people messing around with kieranmillar's levels, and how many features (mostly different types of skills) they have to memorise! Yet, they seem to enjoy it, including some execution-based pain that comes with the fan in Lemmings 2.
With keeping existing features, you do not restrict people in any way to still enjoy the "purist", restricted and more "conservative" type of challenge Nepster Lems, Lemmings Migration etc. have to offer, while at the same time leaving all options open for people who prefer different designs. If we all agreed that we wanted your types of levels only, as great as they are, we could simply go back to playing (Super) Lemmini, because mechanically NepsterLems could easily also have been created for that platform, whereas many other packs couldn't.
Hence, why the need to reduce the number of features NeoLemmix has when these reduced engines are already out there, in peaceful co-existence?
With removing features, in contrast, you slowly transform NeoLemmix back to its roots until your type of challenge is pretty much the only one which can still be created. Which will at some point leave players bored, or at least "annoyed". Playing through your pack is certainly not boring, but at least for me it gets annoying pretty quickly
, no offense here. And I don't mean "annoying" by "frustrating". It's more that when I have just solved a complicated level, click continue and instantly see the next huge open-ended chaos maze pop up, I don't really have the energy left to wrap my head around that right away. I will most likely exit the programm and return to it sometime later... much later... and then it's nice to have something more light and refreshing for the meantime, something totally different.
Currently however, you're taking a lot of this fun stuff away, which will streamline the content which can be created a lot, rather than allowing for an open and free market of ideas, where less popular levels just don't receive much attention, but aren't entirely prevented from being built.
It was sort of surprising to me that among the levels nin10doadict skipped in his LP of Pit Lems, like "Check mate" and "You had it coming", were the ones I had deliberately created in a way most akin to your level building style
. I wanted to create something challenging, taking your levels as a good example, and challenging is what the levels became - with the result of people skipping them ^^. Even when nin10adict did solve the level in the end, he was sure I had created it just for trolling.
Water objects can be resized horizontally in the new-formats.
I don't quite understand what you mean by that. Do you want to change the size of the trigger areas of water? Or be able to do that in the level editor?