Why Don't We Have A New Game Mode?

We could have a mode like Summoner's Rift, but it has Dominion-like features instead. For example, it can be like capture the flag, where you go and try to capture a base on your side and keep on advancing till you get to the nexus. However, it's going to be simultaneously, so it isn't exactly like Nexus Siege, and the bases can be recaptureable. The bases allow you to respawn. What do you guys think of this idea?