Mothballing ships might be a good way to keep empires fighting
Mothballing yards I think would be a nice balance addition for empires that cannot actively maintain a massive military and I think make wars more interesting for endgame when it’s massive empire vs massive empire. Could probably be a star base structure or planet defense structure that adds “mothballing yards” with limited space.
These yards should, again, have limited space. The point should not be to have a giant secret hidden military that was taking up 0 slots but instead generally be older/less powerful ships that you can no longer justify bringing into direct combat or be used in an emergency when your fleet is wiped out.
They should act like real life moth yards basically. Have to take time to get everything back in working order (it could depend on tech level, with older tech being much easier to bring back online vs newer).
I think this would help make wars a bit more dynamic and not game over when your fleet doesn’t jump away before they get absolutely destroyed and you don’t have a ton of alloys right in that moment.