Honestly, one of the only only issues I can find presently with this pack is how it does not take into consideration characters holding onto sonic, in cases such as SRB2 Heroes, or Multicarry.
And the other issue can be solved by adding more models.
Though, I would like to see a fix to endsigns, so that unmodeled characters still manage to line up with them (and so we can get proper reversed background color), but I don't know how feasible that would be. Maybe have the sign by itself, and offset it just enough to have the sprite be drawn on it correctly?
Regardless, this is great, and I'd love to see it expanded upon to support more mods, and maybe have decoration models. I mean, even mania has models for the decoration, and it would certainly spice things up a fair amount. (then again, BSZ's decor is kinda a pain, so...)