The answer was that it is cheating to start with a rocket with slightly less avionics than needed, okay, but that is only 1/3 of the question.
-> When the PVG orbit is complete but I want the still running engine to be used to raise my AP as much as possible with the remaining fuel. (this one may be important)
-> When I start without PVG and decide to activate it mid flight
I am sorry that I open another issue/ticket. I asked why throttle is cut when engaging and disengaging PVG (https://github.com/MuMech/MechJeb2/issues/1848)
The answer was that it is cheating to start with a rocket with slightly less avionics than needed, okay, but that is only 1/3 of the question.
-> When the PVG orbit is complete but I want the still running engine to be used to raise my AP as much as possible with the remaining fuel. (this one may be important)
-> When I start without PVG and decide to activate it mid flight