That just smacks of preparing to fail - hardly inspires confidence in the AA product and further re-enforces existing perceptions.
''The bad news is your flight has been canceled.
The even worse news is that we are going to cart you down to Heathrow in completely the opposite direction and fly you right over Manchester again in several hours time. Have a nice day''
I can think of no good reason for flying out of T3 with a 'premium' offering. The two things are not compatible.