Thankfully none of the levels in this pack requires the use of a direct drop and doesn't use updrafts, switches, teleporters or the new tools. Even vertically-scrolling levels are rare. I think this pack was originally touted as a sequel to Oh No! More Lemmings in a way, and relies on traditional tools and older level designs. There was some question behind the inclusion of 3 of my levels in Armageddon, "Prize Catch", "Overflow" and "JAILBREAK!, because they weren't released in previous patches, despite one being very old (well over 10 years old) and the other being an old contest level.
Yes, I've been thinking about this too, especially regarding the question of finding a builder tutorial level to replace "Play Bridge", but also if we stick with 30 per rank, we may end up needing to find other levels to introduce. (I know we have the levels in the "Extra" rank available, but at the moment I'm only halfway through the pack and it's all guesswork as regards how many levels I would like to suggest cutting.)
I would like to consider RotL to be a "best-of" of the community's work from the pre-NeoLemmix days, and reject any new inclusions that were made later than October 2013 (the release of LPII, which marks the start of the transition from Lemmix to NL). "Prize Catch" is fine because it's from a contest run in March 2013 (and I believe three other levels from the same contest are also included, though my entry "Brute Fours" didn't make it).
That said, I'm not going to look at the levels already in the pack for release dates. I don't think anything is included that's really inappropriate.
Because Lemmix was the main engine before NeoLemmix, most of the levels are restricted to features available in Lemmix, but not all. My levels "Minesweeper Lemmings" and "Lemmings of Persia" were both made in Cheapo, and use custom graphics and vertical scrolling. I'm a bit unsure about their inclusion, but I guess it's okay as kind of an equivalent to original Lemmings' VGASPEC levels.
"Rounds and Swingabouts" also bothers me, aside from it being a level I didn't enjoy playing. I think it might be the
only vertical-scrolling level in the original tilesets (unless there are more in the ranks I haven't gotten to yet). I don't know whether we want to consider that a problem, or let it slide.