That’s not a bad idea, actually 
I can possibly see something like this (just an example)…
Random Epic Battleground (bgs designed to last a “medium” amount of time)
Alterac Valley
Isle of Conquest
Southshore vs Tarren Mill
"Random Siege Battleground" (bgs designed to last a “long” amount of time)
Wintergrasp
Tol Barad
Maybe they could even increase the amount of conquest points for winning a “siege” battleground or something, to account for the increased length/duration of such games.
Seems everyone would be happy