I forgot to mention, but I also chose Mercenary over Cavalier cause I wanted to prevent the team from being taken out easily, and with him as cavalier, it makes half the team easily killable with a beast killer.
I've also been considering a full 10 person team eventually, though I'm not sure who it would include (Trixie, Flurry, Twilight, and...............Heartpury?).
If I did, it would almost definitely include Trixie and Flurry, but then I'd have too much magic -_-...
I would definitely recommend getting the system just for this game. It's that fun.