Yep, controllers are hidden by default, but they are never actually lost... unless you want to dublicate the material :]
"not trivial to set up"- meaning it's not worth it or it's hard to set up or exactly opposite?
It means that i don't know if it's even possible :] You can't expect to simply plug in script or expression controller and it would work, you first have to open them, create variables, assign controllers, write expressions... i think, you got the point ;]