Calculate locally? Can you describe this? You mean, you basically run your own physics implementation? Thats a nice approach, if I understood that correct and definitely would bypass the issues with the other physics-actors in the scene.
There are two options for me, either I run a second physx scene and mirror the original one over to the second one and recalculate physics there and transform the results over to the original one, or I just save the transforms and velocitys of all other actors in the game, mark them kinematic before the rewind, and then reapply the data. And thats what I am doing at the moment. It sounds pretty cheap and expensive in terms of processing power, but so far I tested it with 280 physical actors, including 3 destructible meshes and it worked without framedrop.