As for the Sanctuary System Ludia have designed, in order to make a lv20 Sanctuary, many alliance have co-operate to make them together. And I think it is good to help each other while playing the gamllie you loved together.
But some alliance didn’t have policy to help or co-operate with another alliances to make lv20 sanc, their policy was so easy by sending their members to the alliance that making the high level sanctuary and steal by put their dinos in the slot and then return to their former alliance (surely with the high level sanc) or we can say that their policy is try to steal sanc from others.
My suggestion to deal with this sanc thief are: -
Ludia should give an authority to the first builder of the sanctuary so he can banned those thiefs from tthe sanctuary
Player who was banned from the sanc cannot get any benefit (can’t FIP) from the sanc he was banned (and his former alliance can’t get any too)
The slot that contain dinos from banned player also can’t replace new dinos until the countdown reset