That would just cause them to pump chemicals in you head, I think. But it's definitely thinking in the right direction.

As long as I am not aware of that (or do not dislike it)... well, why not. However, MugaSofer is right, the genie has to understand the (future) utility function for that. But if it can alter the future without restrictions, it can change the utility function itself (maybe even to an unbounded one... :D)