This type of event can't be organized by just saying "be on at this time, trust me" Wargame bgs need a viable comp and team and a leader. All these attributes are especially true when talking about teams that have not played together in a premade setting excessively, ie: nearly everyone. Wargames still have bugs that can make restrict some teams and even more bugs that may not have been found yet.
Kincaide, talking about AP or just a dedicated server in general will speed up the process of making wargame 10v10s a regular event. In the future if everyone starts to play on one server, being ap or not, these 10v10 wargames can happen without a schedule or team-making. "oh 10 ppl on horde, 10 ppl on ally, ok lets do some wsg. Everyone jump in skype". Similar to korgath of the past, ppl log in and can do wargame arena's or bgs / skrims and once there are enough ppl available setting up 10v10s is easy. With everyone being on the same server everyone will get to know everyone and a true community of skilled and fun players can flourish. While creating short-term games right now to test and explore what could be a different meta play-style is a great idea, dismissing the talk of AP and the idea of having one server for everyone to roll on for wargames is probably the stupidest thing to do right now. Ppl will always complain and go off topic with insults or what have u, to avoid an important topic because of some banter is something i dont believe is correct