I just found this thread, and I have to say I'm very excited about the game theme/mechanics you are heading towards. I've always wanted to play a game with a nice discover-it-yourself spell system, and the magic school thing is also a nice and original twist to it.
Some of my ideas/opinions for it, in no particular order:
-Make it more generic than just a 'magical school' game. Think a combination of the randomized and deep magic system with the B12 town building idea with the DF adventure mode, with the options to play in many modes, including: large magic school, small master+apprentice(s) workshop, wizard's tower (like what Toady might add to DF in the long run, with minions and such), rogue wizard roaming the countryside, etc... I understand that this is quite alot to ask, so maybe keep it simple and make only one mode for now (preferably the large magic school one) and add more later.
-Make the magic system quite deep and complex, with many different ways to practice magic. A single general way that works for everything, such as wands being used for all magics, or all magics relying on incantations, should be avoided. Basically, have it be many different magic systems loosely connected to each other, for example:
>Alchemists create potions that can be drinked, oils that can be applied/explode, and catalysts that other mages can use to modify their spells
>Incanters learn the words of power that can modify the flows of magic to create effects
>Diviners see the future in crystal balls/tea cups/whatever
>Summoners/Demonologists use pentacles and incenses to summon otherworldy beings to do their bidding
>Botanists/Zoologists prepare plants/animals that can be used by other mages for their magics (ingredients for potions, reagents of summons, etc), or alone as a poison to apply to weapons and such
Ofcourse, no mage would specialize 100% in one thing. So after years/whatever ingame, the character would have the choice to specialize more and more, and for each specialization he would need certain skill/grades in certain spell systems.
-Things to do other than schoolwork. A large 'outside' world, out of school grounds. Maybe to be explored on holidays? On special school assignments to get reagents/do research? Maybe have a 'credit' system in the school, so that you can take few credits per semester to have more time to explore at the expense of taking more time to complete the education?
-Options for world generation, such as school size, number of students, rarity/difficulty of magic in the world, wether there is an overarching plot (great evil to be stopped, whatever) or just sandbox mode...
-I dont know how far you could go with the AI, but advanced relations would definitely flesh out the thing, making it an awesome sims-rogueling-fantasy hybrid. "Hmm, I'm a bit hungry, but if I go down to eat at the mess hall, I might meet McRivalDude and start a fight, losing time in detention afterwards that I could have used to research new spells/explore the northern volcano for clues about MrBigBaddy, and I might alienate my new friends from House Urist, which I need to keep intouch with to get the smuggled illegal magicl reagents i need..." or whatever.
I myself cant help you yet, still learning the ropes of C++, but if this project remains afloat (which I hope it does), I might join up later on if I can offer some kind of help.