If multiple objects share one mesh, it means that they all play the same animation/use the same vertex controller. Is that, what you have in mind? By default, all will be treated as seperate instances as far as rendering on the GPU is concerced. However, if they share the same mesh, you can give Object3D.shareCompiledData() a try. Just ensure that the object you touch is the source object and that it's the first in the list. I'm not sure how this will work out, because i've never used it that way. It might work...
