I do a few musical things for people's mods, if you have a music request PM me about it (I prefer to make new things than remix though, personally remixes just feel more lazy)! I can't commit to being a full member of any hack's team, but I'll help out here and there and don't request anything for it other than to be credited either on the hack's main page on the member list and/or in-game credits. Cheers!
The maximum for one model is around 5mb space-wise, which depends greatly on the size of textures, but normally 10,000 polys is the max for a single model. That said, by splitting up the models, we can have higher poly models in-game. For example, the Bowser castle seen in the trailer is over 50,000 polygons, split into 4 parts.