I think it's pretty much a matter of someone just starting to compile a pack, isn't it? As far as I can see no one's said "NO! I WANT TO DO IT INSTEAD!", so I'd say go ahead and post your proposals here, so people can comment on what they like about your selection and what not...

Last-minute levels have been included in previous editions too (Shadow's packs, for example), so I wouldn't say there's a need to wait for some levels to be finished either.