@Aqu I mentioned it to you when we were talking about the reset or rewind, whatever you call it, on skype. 

I forgot to mention this before but as it concerns magitech and the mana batteries. For one I was thinking that actually building it would require magic knowledge students would not have yet not to mention the tech part which can be acquired.

As for spirits, as we saw or I hope at least, the table of spirits Bee posted, one can assume there are more and less powerful spirits. Thing is a spirit can use the mage if they are not trained, by this I mean the more powerful spirit can and will not form a contract with someone weaker, not to mention they might just take the mage over. 

The mana batteries... I thought they would or rather could only be used to power magitech devices not mages, but even if, using an external source of mana that is not attuned to a mage can or rather should create anomalies. This should prevent limitless mana pools, in theory at least. One of the symptoms could be drunkenness, I mean that they would get drunk if used mana batteries to power spells, maybe not right away, but the more mana is taken from a battery the more intoxicated the mage becomes.

@Cirus Well a user of a few particular schools can mix them or their effects, but not take it as a different school altogether. Like Bee said, just have the schools that you mix and it shouldn't be a problem.

These are just my ideas so feel free to discuss them. Before I forget, it might be true that magic school threads die out quickly, but the school portion can be just a prelude to let the characters socialize, the combat after or even while at the school can be done in class or as additional quests or simulations. Again just an idea.