(1) Allow the druid to GM the Self and Elemental magics, as you suggest, or(2) In addition to mastery of the Self and Elemental schools, allow them also to master the Mirrored Path magic of the party.
As it is, the only skills that a druid can GM are meditation and alchemy, and that's just about as useful as a chocolate teapot. This is one thing that I think that was better in MM3-5. The druids had their own (nature-connected) spells. Some of them, such as Lightning Bolt, were accessible by other schools as well, but others, such as Walk on Water and Nature's Gate, were limited to the druid and ranger alone. However, these games had a party of 6, and such a scheme would not run with a 4-member party.
My preferred party in MM3 was Knight, Paladin, Ranger, Archer, Cleric and Sorcerer. That gave me access to all magic skills without needing NPCs, together with backup healing if the Cleric got toasted and two Lloyd's Beacon spells for travelling back and forth in the early stages. For MM4-5, I had to replace the Knight with a Thief. I tried a Ninja, but found it ineffective as a Thief without booster items, and a poor Fighter compared to the Paladin.
