As the current number is 146, I think we should aim for 150, probably by adding a few more PSP levels, L2 remakes and maybe ZXS/NES levels (I haven't looked at these yet so I don't know what they are like), and then removing a few to get back down to the round number.
I'm happy with using bsmith's current list as a starting point, since it takes into account the feedback so far. So, in order to avoid anyone having to look again through all 10 pages of the thread, I'll list again the ones on this list that I have reservations about including. This isn't the same as "voting against", since we are currently short of the target, so we should probably decide on additions first, then an appropriate number of removals.
Present 4 -- this may have been included by error, since Nepster originally voted in favour, then withdrew his vote when I pointed out the level contains many hidden traps.
Taxing 18 - we threw out the bomber timing levels. Why add this one back?
Tame 8, 9, 20 -- three Tames is enough, and these three don't contribute anything new.
Frost 13 -- while not completely trivial, not very interesting either.
Covox 8 -- more annoying than fun.
Wild 8 -- uninteresting.
Sunsoft 26 -- requires miner turning on OWW, which will be removed in future versions of NL. Weird to have Part Three before Parts One and Two, but also weird to put it after, since it is the easiest.
Wild 10 -- uninteresting. I remember Insane Steve called this "the worst level in ONML".
Sunsoft 28 -- nothing special. Could be kept or removed depending on number of levels.
Havoc 19 -- hidden traps, probably unfixable backroutes.
Other than that, this looks like a really solid shortlist! I'll list my suggested additions soon; this will take a bit longer as there are more levels to look through