I think DocPanic has pretty nice idea about OL gearing up monsters and getting some additional skills (besides OL cards).
I see it like, for example, an additional deck of cards with some upgrades for mosters and/or condition cards (to make them more powerful). OL would pick one of these cards in the very beginning of the campaign and two more after the interlude (or according to the amount of quests he won in the act 1, win 2 quests = get 2 cards).
Such deck does not need to be big, I think 12 - 15 cards would be enough, just for the sake of variety (OL would not be able to get all of them anyway so he will have to think which cards would be more suitable to his play style or OL cards he has).
I really hope FF will draw its attention to this thread and consider the idea.