I am experimenting with a system that simulates the same results sort of.
After a battle is won, right before the end screen, any unit, ship, etc that is less than 25% health is destroyed. They are there to fight the battle but once it is over, this checks each unit health and removes them if less than 25 % health left.
If it's Red, it is Dead. It works like repair sort of.
Plus to slow down the planet rush, planets actually cost you money to maintain. You must build mines and trade routes to support your empire. This make it easier for a losing side to 'come back'. Of course changes to the AI BUILD_TEMPLATE need an adjustment to prioritize the fact that it needs to build more income producing structures and planets with a trade route is more valuable. Just an idea right now.