Yeah, I could be down for that. I had an idea for a more mundane "antagonist" plot. Basically, Bruce is messing around with alien technology, and someone who's not in on the secret gets their hands on it(he puts some in his car, which gets impounded, for example). 

Now the rangers need to get it back before someone discovers it, but they probably can't use their powers, or they'd further risk exposure. 

EDIT: or, of course, they're seen as heroes and don't want to ruin their reputation by being caught breaking into an impound lot.