a paladin class for my Wessex campaign I went back to the original published version of the class as my starting point and trimmed it down a bit. Today I'm going to do a similar thing to the Druid, starting with the Druid class rules in Eldritch Wizardry and building a prestige class style template that can be overlayed onto one of my four basic classes.
class requirement: magic-user or changeling
alignment requirement: Neutral
ability score requirement: Wis 12+, Cha 14+
equipment restrictions: only use leather armor, wooden shields, sickles, scythes, scimitars, spears, slings, staves, clubs and flaming oil
basic advantages: +2 saves vs. fire, learn secret Druidic language & script
advanced advantages (level 2+): identify plant/animal/pure water, pass without trace
advanced advantages (level 6+): immune to charms from dryads, nixies, etc., assume animal shape 3 times per day (each shapechange cures 2d6 damage)
expulsion: harm an animal not in self-defense, harm the woods
I cut the ability to learn a crapload of new languages, as I don't even use language rules all that often. Also gone is the idea of advancement by combat and the strict hierarchy. I think I still have a Great Druid running the show, but in Christian Wessex the druids are going to be an underground organization without the luxury of being that finicky.
At some point I may import some or all of the druid spells into the game. Joining the druids would be a good way to get access to those spells, but they wouldn't be mechanically exclusive to the class. Like the cleric list, they would simply be added to the one bigass spell list available to anyone who can cast spells.