Interesting stuff.
I think I might have a character concept that would go quite well with this RP.

Base idea: A fake princess. Basically a princess and the pauper situation... sorta. Base idea is that she was a body double/body guard/assassin for a trouble-making princess but helped her escape her royal life/consequences of her actions and took her place for the [s][i]banishment[/i][/s] lovely school trip. I'll admit, I'm struggling with the fine details currently, but that's the core concept.

I also have some leanings towards maybe the real princess dying, and the body double taking her place with none -or few, if any- the wiser. Maybe, the princess was killed by her carelessness of something. Heck, maybe in the course of training to be a body double and basically learning all the things the real princess was, said body double ended up looking like a far more appropriate heir, even without royal blood. So, someone assassinated the princess and arranged for her to be the replacement. Meanwhile, the "sending her to the school" thing is an excuse to explain why her behavior is changed when she returns to cover up the switch.