One thing that bothers me about siege is how the spawn timers tend to naturally spread everyone out. There's less incidental cooperation on siege than on battle as a result of this.
It might make sense to give siege "spawn waves" instead of individual timers (and also, incidentally, tighter spawn locations).
Attackers have, say, spawn waves every 10 seconds.
Defenders have spawn waves every 40 seconds.
You spawn with the next wave, so if you die 1 second before the spawn wave, you spawn right away. If you die right after a spawn wave, you're waiting.
But either way, you're likely to spawn with a few other people and there will be more incidental cooperation on both sides.
This will also help prevent the problem where you die, wait 30 seconds and spawn by yourself in a room full of enemies and die instantly again and have to wait 30 more seconds... at least you'll always spawn with other people.