Yeah, that doesn’t seem like it would work. As Felonia noted, that would just force defenders, but not attackers, to split their forces.
I don’t have a fully baked solution, but I feel like there is a kernel of an idea here: what about instead of time dilation, they use alternate realities. Make X instances of the system and split the players up between them. E.g., if 10,000 players show up, and you can only really handle 2,000, make 5 instances of the system, split the players up between them, if the Keepstar is destroyed in 3 or more, it is destroyed. If it repairs in 3 or more, it is not destroyed. Whatever happens to a ship in whatever instance it is in is what happens to that ship. For anything in space that doesn’t have a pilot, maybe whatever happens in the initial instance is what sticks.
There would probably be problems that would need to be dealt with where you’d end up with 2 instances with all pilots from one side and 2 instances with all pilots from the other, so they’d need a mechanism to prevent that… Probably would be a lot of other issues, like you’d have to come up with a mechanism to roughly distribute classes of ships across the instances so you didn’t end up with one side getting all their logi stacked in a single instance. You’d have to figure out how to do loot. But I wonder if there isn’t some kind of a solution there that is at least better than the status quo, until CCP fixes the underlying architecture.