I voted for vertex weights as i think this a very important feature that is missing. At the moment we use vertex animation for our models but it creates very large models.

Anything that could improve performance would also be on my list. Gamestudios performance is good but if there was anything that could be done to improve it (i.e Triangle stripping of models / levels, Occlusion tests etc) then i would like to see some experimentation done there.