I thought about suggesting group brawl in pve area to customize some out-of-cyrod alluance combat...then I thought about the chaos it may lead to, then finally drop the idea.

But how about Mudballs! We probably need an addon to manage it but it could be real fun.
For example:
12 players in each faction, registered by host addon and each alliance players must dress up with same costume.
Pick a location: Daggerfall, Auridon, Winterhold or any alliance keep/bases.

Players must try to “kill” enemies with mudballs while trying to hide themselves from it. Someone got mudballed will have immunity until the effect wear off. Addon will record the mudball you get from living registered opponent, and the number you throw at them. Any player get throw 10 times will die and his/her mudball attack no longer counts.

And the last alliance with survived player wins the game and conquered the land nothing real benefit （or players can discuss it themselves）, but it can be fun and “montize” alliance war outside the cyrodi, as it should be

Does it sounds fun to you and any addon makers are willing to create such addon?