What do you mean with heavily integrating physics in your engine?
do you mean that you are starting your own physics simulation or are you still using bullet that you mentioned in a previous post?
anyway , the idea of moving the physics to a specialized hardware is a great idea as you suggested !
it would allow because of the higher processing capabilities , much more detailed simulation ......like you would be probaply able of simulating a model(like a tree or car ,etc...) as many smaller models , you would have a group of tiny models which are processed independently that together form up the bigger one(car,human,tree,etc...)
and then if the car for example crashes the individual smaller pieces of the car would fall apart or even deform like in a real accident!
As someone said : imagination rules the world!