*peek on the wall of texts*
*faints*
The world concept can be anything, so I won't comment too much on that.
For class system, I like the idea of having a few "base" class, and then specializing began depending on player's play style. The AI idea seems fun.
Or you can give a generic character at first, then let the players assign abilities and status. The limit might be tech tree which requires mastery in previous ability to unlock stronger ones, or limited points to assign on ability levels. Thus we can see specialized player in one particular field, or able-to-do-all character which can do anything but weak because all of the skills are low-leveled.
Also...I am thinking to role a healer class or something...maybe...*slither back to hiding place*