After seeing the Combat Live Stream with 3 players sharing a planet to start with. I realized the awesomeness of (albeit probably hated by faint of heart) of an 8 player planet map where the ultimate game ender is the first to successfully get to space, get the Commander off world, and smash the left behind homeworld to bits! Now this obviously would be a strategy in any round that starts a planet, but possibly one catered with the intention of ending a round in 30minutes. Players utilize a balance of working on teching up to space while maintaining the defense and harassing of other players in the round. Again, this will probably be achieved with the game settings just set to regular FFA to begin with, but perhaps if this was a single planet map surrounded in astroids, once the majority of players left on the smoldering husk planet are gone, those that got to space engage in a final showdown of cosmic pinball. I know alot of folks are not into rush mechanics, I myself am not; but sometimes I like to have a good quick round with my buddies, this kind of deathmatch debauchery fulfills my less mature gamer side. Still solely anticipating the Galactic War (insert "The Galactic War" quote from kickstarter vid)
I am generally in favor of all the specialized game mechanics that people are coming up with, such as this one or "planet-hopping out of a black hole", as someone else suggested
I think things like this (and more) will be easily accomplished simply by making a map a certain way without the need of additional game modes.