Okay, serious questions.I came across the issue because one of the modifications I was making was the ability for a magic user to prepare one or two spells ahead of time. To hold them in readiness, to steal a phrase. I was worried that would give magic users the ability to kill a combat by going nova in the first couple of turns. I think I can put reasonable, and logical, limits in place that will allow magic users to have a few spells held in readiness (at a cost) but not nova the combat. And my version of path magic makes it possible to cast spells much more quickly but, again, at a cost. We'll see how well I manage to balance this.
1) do you actually own Thaumatology? Path Magic has the idea of mages who can skip the need for rituals, components, and prepared spaces entirely. But more importantly it doesn't really have combat suitable spells, which is mages need other skills.
2) why on earth does combat magic have to be a thing?
3) seriously, what's wrong with the standard Fireball spell. Charge for up to three seconds spending up to [Magery] Fatigue per second, release on second one, two, or three, when it hours the fireball does one d6 of damage for reach Fatigue of charge.
4) seriously, Thaumatology. I've got a setting tucked away that uses the 'spell slots via modular abilities' rule, a heavily controlled spell list, and no prerequisites for spells. Spell does cost 8 points per slot, with the option to spend more CP to increase your skill with the spell.
5) additional rules breed additional problems. The less moving parts the less chance something will go wrong.
6) have I mentioned that Thaumatology is a really good book?