Hey captain! While I'm a super mod here, I do try and involve the whole community in decisions. But I do have some thoughts about your suggestions.

Any% NG+; There's not a lot of difference if you do NG or NG+, other than starting with a faster ufo. However, could be interesting for a 2-star run.

All Levels: We have that in the form of Hat Trick Master. It also requires you to 3-medal every stage.

All costumes: This is really close to the definition of Feats of Glory (what we call 100%), with a few minor things added.

I recommend getting discord at some point, as that is the superior way of effective communication. Forums here are hardly checked.

Edit: Since the requirement for a certain feat is to just do all of them, not 3-medal, the idea would be just doing them.

1: what I said 2: Like I said earlier, that wouldn't add too much different.

3: Yes, but the categories would be close together.