Warfare is an Anathema to the Monks. They don't carry physical weapons, relying instead upon spiritual purity. They devote themselves to fighting demons, not their fellow man. Although they will defend themselves, they try to be non-violent and won't kill a foe if there ins any chance of ending the conflict peacefully. They wouldn't even kill a werewolf, choosing instead to tie it up and go on a long quest to try to find a cure for lycanthropy.
Paladins are quite different. They use physical force to fight evil, and won;t hesitate to kill those who have sided with evil. Paladins are more fanatical and Law oriented, while Monks are all spirit. As you probably know, Junil, the god of law, and Sirona, the godess of wisdom/spirit, don't get along.
That said, the Crusader civilopedia specifically says that old Crusaders often weary of war and choose to live out the rest of their life fighting spiritual foes. Logically, they should upgrade to monks. Of course, currently Crusaders are the stronger unit....
In my version, Monks will be available at Mysticism. They will have 1
(since I'm giving the Elohim leaders Spiritual again they will start with mobility) and 1/2
, but will also have at least 1 Spirit affinity (which gives holy strength in my version). This means they can be quite stronger later in the game (especially vs demons) without needing an upgrade.
I was thinking that it would be good to make them either be unable to attack or to have a combat limit, but only if I could figure out a way to make that only apply against living units. They shoudl still be able to kill demons and the undead.
Although they won't really need an upgrade, I'll probably let then upgrade to Priests of good religions (certainly Vicars, probably Confessors, Stonewardens, and Priests of the leaves too) anyway.
I'm also thinking that I'll give every civ a powerful and particularly thematic (sometimes requireing the most appropriate religion, civic, or alignment) unique limit 1 national unit. The Amurites will have the Cassawallen, the Bannor the Patriarch of the Order, etc. These will all be upgrades with very high level requirements, and will basically be a second national hero that can be replaced when killed. It is more a heroic rank than a heroic persona. Of course, many of them will probably actually be the rank held by some of the actual leaders. The Elohim's would probably have to be the Head of the Order of the Elohim Monks, probably called The Logos. Naturally, it would be a Monk upgrade.