The other thing I wanted to ask (and this seems to be an obvious answer) is what do you think would possibly be the best 'class' for a character who was to be RPed as a druid? The problem I see with the Adventurer class is that being non-noble, anyone can execute one for any reason, which not only proves to be a challenge but can also be a bit silly. Additionally, though I could envision such a thing in real life as well, nobles will treat them like dirt if they are Adventurers
It does open up some interesting ideas though, where the 'Archdruids' could be the priests (nobles) of various realms and the lesser druids would be playing as adventurers, running around, fighting evil, dealing with sages, etc. It all sounds well and good but getting people to join would be the tricky part
The non-aggression aspect has some similarities to the Church of Humanity in that they don't use the more forceful religious options, but it sounds like you'd want to take it much further. The immediate challenge I can see you having for the RP is reconciling the fact that most of the nobles you could potentially recruit will be warriors who won't follow a pacifist faith. Of course, you could make it a faith for those who abandon violence to become courtiers, traders, etc. But that would mean you'd probably have to accept it would have a small number of noble followers.
But it's feasible and it could survive. For survival, you just need to find nobles willing to covert and then others willing to allow your temples to stay open once they govern the region. One way I can think you might do this is by making the religion a sort of realm-neutral diplomatic corps that commands respect from all parties. In part, that's how the druids operated in pre-Roman Britain. Of course, the British druids were also so powerful that they could walk between two warring armies and tell them both to stop fighting and go home. And the armies would do as they were told... unlike BM players 
That is actually what I was thinking as well, and I am glad you brought up the pre-Roman Druids and the power they had over the various warlords in their land. It certainly is an impressive piece of information and I wish I could find more about it.
It is also a surprise, and interesting, to hear that a similar idea has already been tried on BM and I wasn't aware of it. Still, this does at least give me a little bit of faith that the idea might be feasible
But yes, what you described is very similar to what I had in mind. I like the realm-neutral aspect as you mentioned.
There used to be a religion on Beluaterra called The Living Earth that was similar in some respects. They worshipped Zisa, the Earth Mother and they were pacifists too. Consequently, it was a very small faith. I was briefly a member and it only had a few nobles and a smattering of temples. But they had managed to carve themselves a small niche in Mesh over some years. So what you want to do is possible, but it probably will be a struggle.
Another religion I never heard of, but it certainly is impressive to hear that they did manage to carve out a nice little piece of land to call their own, more or less. Thank you for that valuable information, I do appreciate it
