I have always only played with Battle Style Set so Mania mode is the thing for me. The range of 5 - 15 seems a bit too large though so I'd keep that 5 - 10. Trainers with each pokemon raised by only 5 levels would be easy, but trainers with each poke raised by 15 would be pretty much impossible to defeat. Instead I'd suggest inability to use potions, revives, restores etc. (battle items should be ok though, they are useless anyway) - That's how I've always played the main games and even Reborn to raise the difficulity. In Reborn Battle Style Set + inability to use items proved to be very chall