My assumption of the spell system is that we will get to choose ranks in various schools, similar to MOM and a few others. This gives the Sovereign some hard choices which is always a good thing. Do you go after one branch to get the higher level spells? Or do you branch out to get pieces here and there for some synergy?
If this is the dynamic for choosing spells I’d like to see subsystems between the ranks chosen for the various elements.
Example, a Sovereign takes all 10 ranks into Earth. Thus he can reach the 10th level spells eventually being able to pull chunks of earth from the skies (Asteroids) and launching them at enemies and cities alike. Eventually, he will get every spell that earth magic has.
Now say the same sovereign takes 5 ranks of Earth and 5 ranks of Fire. This will give him access to SOME of the earth spells to lvl 5 and some of the fire spells to the same level, but not all as if he went directly with one element type, but what it does open up is the subset of spells with that combination. So, now that Sovereign can use spells like Magma, or Volcano, while those spells are not available for the Sovereign that chose Earth, or just Fire with all of their ranks.
Resistances are based on the level chosen. So a full earth magic wielder it's easier to penetrate any creature with Earth resistance(10 ranks), while the earth/fire user will use the level of earth magic ranks they have purchased.(Earth5/Fire5).
This type of system I’m sure is more difficult to balance and get right, but would make spell choices an interesting process, as well as adding re-playability factor into what types work best with which strategies.