747Focal what enlightenment!
I happen to be one of those people who believe that my time should not be up unduly early, thus whether in flight test or transport flying, pilots should always maintain the required professional approach for the task.
I may not know much, but it is probably sufficient to judge that the limited knowledge and attitudes that you hold and represent would not be sufficient qualification for any involvement in my flight testing. I suspect from my acquaintances with alf that he would also agree.
For the thread, what about engines over and under – Lightning? There probably was a small pitch effect with one engine inoperative, but for practical purposes there was no noticeable effect. Thus thrust asymmetry is only significant on a longer moment arm and, as discussed by others, it would be impractical to have lengthy, heavy ducting to overcome the arm length. Aerodynamic force from a rudder is a far simpler solution …. unless you have no fin to hang a rudder on – B2? Most tail-less aircraft also resort to aerodynamic control to create counter yaw forces by using aileron / spoiler.