Sure, the exploit comes in because you know exactly when a spawning civ will be at its weakest state.That is simply a strategic maneuver, rather than a exploit though.
Of course a player is going to attack at the target's weakest state.
What exactly is different about edead's spawns?can you implement edead's spawns, trying to take out a spawning civ in soi has its own strategic implications. It can be done but is more difficult with the reinforcements.
or could you add a unit upgrade that gives defensive bonus, +100% defence for new civ, which expires after a few turns.
It's not an outright ban, you can still destroy spawning civs when they claim parts of your territory (by refusing the flip, which is still possible of course). It's just intended to stop the exploit of spawns as a means of expansion.I think a way to make rushing a spawning civ difficult but still possible is preferable to an outright ban.