[HoneyBadger]

A way this could work, somewhat, would be if mages could be linked individually to spells that only they themselves could cast. So that when the nation as a whole researches say Thaumaturgy 6, your specific mage type (sorceress Suzie, let's say) gains a special spell that only unique sorceress Suzie can cast, above and beyond what generic mage Bob and all the other generic mages can cast, even if they have the same paths as Suzie. It would be sortof like weapons, where you assign general units an axe, for instance, but you assign a hero a special, unique axe that nobody else gets-except this axe only appears when a certain research prerequisite (which could still be 0) has been met.