I believe Mech Assault tried something along these lines.
They had a galaxy map with over 50 planets, 50 or 100 I don't quite remember. Anyways, you could join one of five factions and then wage war on a planet. Essentially when you fought on the planet it would be like a regular game, 5 mech vr 5 mechs or whatever you wanted. When you one the battle, your faction took 2% hold of said planet.
Well to say the least it turned out to be fairly flawed. I think the way they are taking is pretty good because people get to feel a pride of ownership in their land. It will feel really cool working your ass off for your own kingdom and then taking territory, fighting to hold the lines, ect. In Mech Assault you never really felt that.
The 2nd issue was that everyone just joined the winning faction. So for example "the green" faction would control 50 % of the planets and 80% of the general population playing the game.
Lastly most people didn't care for the game type so they just played regular quick matches. I hope having more of a personal investment in your territory and kingdom might sway people to playing the persistent version. It will be definitely what I am playing