My guess is that you don't need something perfect to acheive 90% success. Maybe you switch to real-world physical training for the last 10%, but the first 90% (or whatever) of the neural network training - learning which 'mental' control corresponds with which 'muscle', getting the grip close to the right place with close to the right force, getting an approximation of sensor feedback into the network (with some noise added, perhaps) should get a long way there. I mean - you can see the terrible simulation they used for that asimo robot neural net training - not anywhere close to a unity simulator. I did just happen across this: http://gazebosim.org/ Which seems like it's basically designed for these sorts of things.