Well try to cater to two specific classes, but if you put in "must be able to cast arcane spells of 2nd level" that's any arcane caster. Must cast prep spells is wizard, cleric, wu jen, etc. See what I mean? Have your target two for the optimal/intended entry, and if anyone else can squeeze in then the more the merrier.
I need to change my plan then, my incarnum/tob Prc is too open and I don't want to force a specific entry on it. I'll probably post it outside the contest at some point. I have other idea anyway.