Yeah, pure RPGM is such a lame thing. That's why most rpgmaker games looking similar, almost as clones. Still, your job is done, and done in a very good way, there's not many RPGM games as good as RoI.
P.S.: hidden characters may sound like a good idea, but in game they're simply not worth try because your team is already strong and well-built and because they have no significance for story