I don't think they will go that route. That would just be artificial difficulty. Reborn is a game of strategy, not a game of unfair bullshit (although the Serra battle can go frick itself). You don't need an OP mon, that you can't possibly beat due to limited resources, rather than strategy,. And no, the Garchomp battle at Mt. Pyrous doesn't count, since you're not supposed to beat it. Making that kind of stuff wouldn't be healthy for the game, and it's well known "fair difficulty".