I understand that but I think you will find you are forcing your user to work in a cognitively disconnected way.
Mentally, for me anyway:
RMB is "do again"
and Escape is “stop doing”
This is easier for me than
“RMB is do again but sometimes, stop doing, but only when you have what you want… sortof.”
Escape works every time for ending a command… whether it has completed the task (but command is still running like trim) or whether you have decided you do not want to complete the command. (Like a tweencurves you don’t want anymore)
I think when you’re flowing you don’t want to have to think about which way you need to end the command. You should just be able to end the command the same way every time.
And somebody correct me but I believe the escape key is the only way to kill every command in a single stroke. It’s a physically bigger key and away from other keys on my computer so it’s easy to strike quickly and not hit other stuff. It’s also just a generally more convenient spot for left hand.