The problem with having Clan Battles on normal servers is that (assuming) two clans decided to have an 8 Vs. 8, it would be hard to actually manage to fit every single player in AND make sure that they don't get kicked - they would practically be forced to buy donor for such an event. Of course, this does benefit Chad and the community in general, seeing as it accumulates more $, but these servers are Free To Play; I don't feel like extra money should be input just to participate in clan battles.
A while ago, #Phoenix had a clan battle with the old #Pegasus which (originally) consisted of 3 rounds. We played the first round on normal servers; it was literally impossible to get every single player on the server, even in the higher numbered au servers (au35-au39). We were forced to play AS servers which, in my personal opinion, was less than enjoyable.
I do feel like something like this should be implemented but it would have to be thought about thoroughly and efficiently and just generally be more organised; there are, as a number of players above have stated, a numerous amount of questions that need to be answered for this to work.