G'day xxgunnerxx,
Years ago when I first started on the B747-400 we finishd a sim session a little early and had a bit of time to play. The instructor set the a/c at MTOW and the temp 30 degC then during the takeoff run had an engine fail after V1 and the other one on the same side fail at VR. So a double asymmetric engine failure at max weight on a hot day.
It was a handful to say the least and if you followed the flight manual it resulted in a gradual descent into the ground, however if you selected the flap up from F20 to F5, regardless of the speed, then there was a huge reduction in drag and the a/c would eventually accelerate and climb away as you cleaned up further. Once you got it clean there was more than enough thrust to complete the approach.
Second paragraph, if the take off is rejected the captain takes over, however if the take off is continued and the FO is handling things well he continues to fly and set up for the approach, though in my company the captain has to do the actual landing.
Regards,
BH.