Considering that the planes themselves often park almost next to each other, has there ever been consideration to providing an airside link from T5C directly into the Central complex, thus avoiding such a detour?
I think T5C is just as close to T5A as it is to an already overcrowded T3. I am not sure whether the trains have the capacity to manage the volumes going both ways. In an ideal world T5 and T3 might be linked they have to put the fire station somewhere so a T5D is apparently out, added to the fact the current transit may not have the capacity.