FWIW,
TMC will never allow a motor to be in a full-step position.
The only exception to that rule is when you are using the 256 microstepping.
(yes, even with “disabled” microstepping, it will just use the middle position between steps).
So, Klipper can’t make the motor be in the full step position.
Nor is there a simple solution to make them stay in that position.
To make it work with XY, it will only work on a simple Cartesian kinematics, also known as a bed slinger.
Because on the other kinematics, motors will be coupled in one or another way.
Making it work on Z will be really tricky. I think you made a lot of assumptions here.
With lead screw, they should be installed in same phase across all motors to make them align.
They should have a good enough reduction ratio and/or friction to stop motors from spinning without power.
Then, there are Z TILT, which most probably make them out of sync without high precision assembly.
About the concept as a whole, motors are designed to run at a specified current.
Drivers are designed to run at a specified current (There is a sense resistor value for that).
So, I’m not sure I really understand what you are trying to achieve here.
You are right, to not drive current and not make motors/drivers heat, there should be a closed loop.
But generally, during printing when everything moves, I do not see a big gain from such complications.
There is a long read about microstepping, precision, current & etc.