Interesting. I think the response would be you shouldn't ride the bike that ladden in traffic if you know it will cause you that much of a problem.
The trouble is when you are touring fully laden with panniers that is not always an option – the answer is you accept that you are slow and lumbering – you do not run red lights – because you are slow it takes longer to clear a junction – anticipate the red, make yourself big and control the traffic behind you and stop early otherwise you are in danger from traffic jumping the green phase across you
As to starting off – anticipate the green and make yourself space in the traffic so you do not have to unclip –do not ride in the gutter - make yourself big in the traffic so that you have a vehicle sized space – learn to automatically select the right gear – learn how to be clipped in properly by at least the second pedal stroke – learn to be thickskinned