Ah, an old question
It seems like there is no way to skip the endless burning procedure with Principia installed, which in fact made it impossible to use low thrust engines. I saw the your disscussion with @FreeThinker on the compatibility with the PersistantThrust mod in 2019. But now the Principia maneuver planner can predict trajectories taking burning procedure into account, I'm wondering if Principia could go further to implement some kind of "burning accelerator". I really want to use ion thrusters in the n-body gravity powered universe......