I’m sure it’s possible. The first thing that comes to mind is this; the RTL point is established wherever the APM is armed. The APM will only remain armed for so long in certain modes before it disarms itself due to inactivity. You would need to change that in the code so the APM would remain armed and waiting for inputs.
I am new to this and learning, so way i have it designed is the 3 arms will be against the rocket while going up and then it deploys the arms when the shoot opens, when the arms deploy they will have the props truing to guide the rocket back.
When you say the “APM” you mean the system that controls the return to home ?
Also i am guess that from home to how ever any miles up it wont care that the props were not spinning from home to wherever up to bring it down?