I’d hate to see this happen. Even with a T5D it doesn’t solve the fact that T5A, the lounges, and the train can get overloaded. Perhaps the later two can be fixed with more than two trains operating at once and new lounges in C and D (would have to include at least one more F lounge) but I can’t imagine trying to pump more people through arrivals and the FCC at peak times.

Also - with the slight exception of the first wing over T3 fast track and the CCR over CX F - T3 is a better and more efficient experience even if less modern.