Sorry for taking so long to get round to this. I've had a look through the pack now, and I think as regards selection, the current "main 150" is a very solid selection and there's only one more change I would suggest making: Havoc 3 "It's the price you have to pay" should be dropped and either Mayhem 21 "With a twist of lemming, please" or Crazy 15 "Worra load of old blocks" re-included.
Reasons for this change:
* Minim was the original proponent of including Havoc 3. On page 12 of this topic he says this was "only in case of emergency", i.e. it could easily be scrapped in favour of a different level.
* Havoc 3 is not a very well-designed level, with too many alternative solutions / backroutes.
* Pro Crazy 15: The main solution is interesting (as Minim noted above; Flopsy also noted this much earlier in the thread). The main thing against is the hidden traps (however, you discover them very early in playing the level). There are alternative solutions, but they are harder than the main solution, so not really backroutes.
* Pro Mayhem 21: namida is in favour. The solution is interesting, and the annoyance of selecting a right-facing basher is fixed in NeoLemmix. The main thing against is the annoyance of assigning 50 floaters. In NeoLemmix we could change it to a floater-spawning hatch (though maybe this is a bit "off" as it introduces a new mechanic for a single level).
* As an alternative, I've suggested using the SMS level with the same terrain as Mayhem 21. This has an interesting solution that requires building a landing platform instead of assigning 50 floaters. There hasn't yet been any discussion of this proposal, so no points have been raised against.
Regarding namida's comments on the other "Extra" levels: fair enough, some of them are somewhat interesting, but re-including any of these levels means dropping one of the current main 150. Except for Havoc 3, I would rather keep all the current main 150 in preference to any of the Extras.
* * *
Now onto ordering. A quick look through the pack suggests that Rank 1 is fairly solid, but the other ranks have many cases where I disagree with the ordering. I think the best thing to do is to make final decisions on selection and Rank 1 ordering, then look in detail at which levels should move up or down a rank, then work on the ordering within each rank.
So for now I'll only comment on Rank 1. Only two levels here felt out of place -- the same two namida highlighted, "Across the Gap" and "Dolly Dimple". These are not Rank 1 levels.
Moving them up means two levels have to move down. I would have suggested "The Stack", but I see namida disagrees. Instead, I will propose "It's lemmingentry, Watson" and "Going Their Separate Ways" -- the latter is a memorable level that would be suitable for being the last of a rank.