Gnorman's Complete E6 Compendium

[Morph Bark]

some ideas from my side:

- there could be something like advanced spheres, which need some inferior sphere as prerequisite.
f.e. the normal healing would give the cure spells, the better restoration, cure blindness deafness, remove curse.
This option would give the opportunity to trade versatility for power and vice versa.

In a way, that sounds like one of the principles behind Shadowcasting.