Essentially AB with actual alliances.
The AB that we have now would not change, but rather a seperate, organized AB will be available just like GvG battles are, except it might be a bunch of members from several guilds of one alliance, or 12 members from one guild in the alliance.
There could be an observer mode/ladder/etc.
Leechers wouldn't be an issue.
No more "4-4-4" "capcapcap" "1vs1 n00b". ( At least for the organized ABs anyway ^.^ )
It would be great to play AB against an organized or even semi-organized team rather than ally/battle with wammos using mending and frenzy wanting to 1vs1 everybody they lose to.

To counter the fact that people could and would abuse this, a faction cap could be introduced similar to Zaishen Arenas.