Could you not give the Dryad and Hamadryad a specific charm spell with a new name and give Druids immunity to that? But then, the Hamadryad didn't attack us in your mod. Is that because you fixed her not to attack Druids? Every other time I've played she Dire Charmed us, regardless of party composition.
I was thinking of the First Edition Druid spell progression. If it can't be changed, the only thing that could be done would be to craete a magick items that gave all the missing abilities, tied to character level. Plus the level of some spells would have to be changed and he'd have to be able to cast 2nd level spells at 2nd level, 3rd at 3rd, 4th at 6th and get 7th level spells at 12th level etc
Is there a 1E mod around?
Cheers