At this point, I wish I had a PULSE Meowth myself. Most of the good stuff in this game is expensive as all hell.
I would've thought you'd have gone after Terra for the finale, but eh. Brooding on a mountain and getting sent on a mandatory holiday to Hoenn is fun too. (Probably not gonna be much fun for long if it's vanilla Omega Ruby. Even in a nuzlocke, that game is a joke.)
Honestly, I've always wondered why nobody has thought to throw these gem-key things into the middle of the polluted lake. I mean, there's no way in hell you'd be able to find anything in there. Key's gone for good and Reborn is saved. Or hell, cast one into the fires of Mount Pyrous. What good's a key if it's been completely destroyed? I guess the sentimental value outweighs the need to keep the damn things away from Team Meteor to these people? Only real reason I can think of to not toss them somewhere the Meteors can't get them.
Or hell, they could try and get fakes made! Team Meteor might end up being fooled by the fakes... until they try to use the damn things(or El sees them). But at that point, they would've already been used as bargaining chips or something, so whatever.
Really, the most sensible solution for the whole "team meteor wants the things" situation that any character has suggested so far(in the game, not this nuzlocke) is "fly off into the desert, away from Team Meteor." But even then, there's been some weirdness going on with the train tracks in the desert(I forget exactly what was going on out there except that it resulted in a large portion of the desert being littered with train parts and the tracks being rebuilt further away from the area each time), so there's no doubt Team Meteor is out there. Because who else does this kind of thing?