So I'd like to figure out if 3D work could improve his "costume" perhaps making a realistic giant bug. I was thinking about planting an actual shell onto the back of the costume and tracking his movements.
My questions are:
1. can MAYA do something like this?
2. does this sound like a reasonable correction/fix?
3. and how long would this kind of thing take?
This exactly the kind of thing you would use Maya for.
In this case you would need to model and texture the Shell in Maya and then match-move it to the actual character. It might also help to model and texture a few extra arms onto him.
As for how long would it take.... It just depends on your proficiency with Maya and your understanding of complex VFX and compositing.