Huge fan of the game, but the destruction of all of a surrendering factions worlds is a gigantic bummer. Some of those worlds were (in my current game) Class 16+ powerhouse planets which I was preparing to conquer or assimilate. Now there is just a huge area of worthless real estate.
Why not -
a. Provide a path to restoration of a planet's former greatness through a dedicated starbase or something, or
b. Set the planets back to neutral, creating a mid-game colonization rush as factions fight over the remains of the former empire, or
c. The remaining worlds, minus the homeworld which was given away, reform into their own, possibly the same, civilization with a specified term of peace which allows them to rebuild similar to the pragmatic ideology 50-turn peace plan, or
d. Something else that doesn't create vast wastelands
I have a game running as a test in which I disabled surrendering - the result is that as one faction gets successive wins they become so much larger/better/stronger than any other faction that nobody can stand up to them. Under the old system, as a faction gained strength the losers would often surrender to the winner's enemies giving the game as a whole a shot at balancing out for the short term.
Overall - the old way of playing the surrender events was much better than it is now. Yes, when somebody surrendered 50+ mediocre planets to me it was tedious trying to re-organize their mess, but it was at least tediously fun. Under the new way I only get a single homeworld which has been fairly useless. Especially the one that was literally on the other side of the galaxy and got invaded before I could even think about sending any ships through a few enemy territories to defend it. Building a shipyard and building a fleet wasn't fast enough either, especially without any other shipyard sponsors.
Maybe when a faction surrenders its homeworld, the remaining planets can (either individually or by solar system) "vote" to join one of the other remaining player, minor or major factions, who then must pay a per-planet "acquisition tax" or refuse the planet. Any planets that are refused by everybody could then go dead or whatever. A bit like a bankrupt Monopoly player, I guess...