Can a clan be split among teams?
If not, then there is at most one defending team. If it can, balance is still broken. Unless you are fine with ppl sabotaging games to win the meta-game.
If there is no defending team (because fight is team(fac W+fac X) vs team(fac Y) on a planet owned by some player in faction Z), then why would structures be anywhere but in the middle of the map, as it is now? If pw structures positions were persistent from game to game, I would understand the hidden meaning of your questions.
If the planet is not owned, how could there be a defending team?
If fight is team(fac W+fac X) vs team(faction Y); planet owner is a player from clan C; clan C is part of faction W; no player of clan C plays this game, then it can be decided whether team(faction W+X) is considered defending or not. It could be, but it could also be argued against. A choice has to be made, a simple static choice, or more dynamic based on clan diplomacy. But clearly, team(faction Y) cant be considered defending...
Is there a case that is not covered?
Resurrection should only be allowed for defending team. Unless you want to mess with planets harboring structures from multiple clans...