Alright.
I think the idea is very cool like a lot of other people, but i can also see why you would be afraid that it will take away from RP.
I think you can have normal mobs spawning as we had once back in the day, just with some simple drops for the players willing to kill them, a few minas, an iron ingot rarely, some bad tools. Here maybe having the hunting skill could give you some advantages over other players without it.
For bosses, i think these should be restricted for the ET. Like they would organize a hunt, BUT WAIT, to track down the beast you would need to have a hunter of x level, and then the people who would want to take part in the hunt would just follow the hunter. Also having the ET control the bosses means it won't have to always just be a mob you fight in PVP as the boss, but it could also be an actor, and the party would have to fight it RP.
I think a system like this would be great, having bosses available for anyone at anytime would simply take away from RP and make the server a little to much like WoW, in my opinion.