I hardly think robots will be a playable race, especially if its after tactics and even if it is during tactics they would have to fallow the fallout canon and destroy the robots after a while any way :/
Robots in general follow a program and doesn't do anything on their own and are also pretty rare, they don't wonder the wasteland randomly, they usually stick to the place to where they were designated.
Super mutants on the other hand could be playable, lots of talking about this on other threads and I'v put up suggestions there as well.