Suggestion: Must kill all champions after base destroyed for win.
To win a game you must destroy all the towers, the base, and all enemy players "after the main base is destroyed" for a win. Once the base is destroyed players no longer respawn, the guns shut down as well as the heal/mana regen, and the fog of war is lifted exposing all the team players that are still alive. I think this would improve player satisfaction, improve winning objectives, and overall fun.
*Edit, to assist & quicken the end the minions then all follow towards the closest surviving minions or champions.