Oakape thank you for your great answer The scenario the have for us is dispatching with one center tank inop low vis and 2 rwy out in Madrid BCN cavok.
Option do a low vis approach or divert. One will be risk of missed and making your cg problem worse The other your accepting to take a bigger cg change. No right or wrong both are acceptable as far as I know.
But I thought it an interesting scenario and greatly appreciate your answer!