Okay, so I had a strange hypothetical situation pop into my head. I could probably answer the question myself if I was more into pokemon, but:
1. Enemy pokemon uses Mean Look. You can't switch out.
2. Enemy uses Taunt, which if I remember correctly, means you can't use anything but damaging moves.
What if your pokemon knows four support moves?
1. Recover
2. Light Screen
3. Baton Pass
4. Yawn
That'd be a really weird set up, but imagine it.
Does the battle just LOCKUP or what?
Uses struggle, maybe?
Good question. ._.
*edit* Probably just an annoying amount of "You can't use that right now" every time you try to fight.