Using a drive that only takes final position

I'm struggling on this one. We have a ethercat integrated stepper motor that only takes in a final position input.

Short of using M67 and connecting an analog input pin to the motor command position, is there a way to have one of the gcode positions output the final position and essentially ignore the trajectory planner for one joint/axis?

I don't think you need to. Just give it a new "final position" every 1ms and it ought to just work.

This is exactly how the STMBL drives work in smart-serial mode.