SSG
Vssg is really refusal speed, a well-known concept, see also accelerate-stop.
Au contraire, my corporate jet engines (GE, RR and Honewell) are "on condition", it is a very nice selling point indicating lower costs. One of our models has flex power built into the FMS perf, btw.
BTW, after 4,000 hours in the C-5, we frequently did reduced power take-offs even at high gross weights when performance allowed. In fact, we weren't allowed not to except in exceptional circumstances. Not even to bring V1 up to Vgo. I thought it a good idea for all the reasons detailed here.
GF
You're general aviation mindset really needs to be open to life in the big leagues. Light twin ideas have no place in transport category airplanes.