Okay, time to wrap this up.
Eight people voted, which is fewer than I would like for such an important decision, but just about enough to give me confidence in making the call.
Six voted for keeping the pack at five ranks, which is a sizable majority, so that is the final decision. Five voted for a smaller number of levels (160 or 162) and the other three voted for both a fewer-levels and a more-levels option, so again, that's enough of a majority to call it for sticking to a smaller number.
So, we will stick with the current setup of five ranks, 32 levels each, and that is absolutely final from here on.
Regarding the recent discussion of possible levels to add if we did add some more: several decent suggestions came up, but none that stood out as must-haves, especially as it's now agreed that the official conversions of the full original levelpacks will remain, so all the levels excluded from Redux will still be maintained in NeoLemmix.
However, there's one possible inclusion/exclusion I want to settle with a separate vote, and then this discussion is completely wrapped up and we can move on to talismans (as well as other possible changes, if any). Of all the proposed inclusions, "The Boiler Room" stood out as having fairly strong reasons for inclusion, and ranked joint highest in the recent vote. "It's all a matter of timing" is the one level I would consider dropping, partly because it's not especially interesting as a puzzle; partly because it's problematic because of the stacked hatches (although the separate discussion topic seems to have reached a consensus that stacked hatches are okay, it's a bit weird to do this for just one level).
Obviously, there are arguments on the other side as well. In favour of including "It's all a matter of timing", it is substantially different from every other level in the pack, and it's interesting to have a builders-only puzzle. Against "The Boiler Room", there is a previous level ("Don't leave any Lemmings" from Genesis) showing bombing through a ceiling, so it lacks some of the shock value it had in the original game.
So, yes/no vote on whether we replace "It's all a matter of timing" with "The Boiler Room".