I think it's problematic for the focuser to change the direction of its numbering - either in its own numbering or via ascom - because you would really want to change the current position number also.
If the range of the focuser is 0-10000 and you are at 1000 - and you suddenly say the focuser is numbered the other way - then the new range would be -8000 to 2000.
Alternatively when you changed the numbering you could cause the current position to change also - so the range is still 0-10000 but instead of being at 1000 you would suddenly be at 9000.
My FocusMax system does not allow changing the numbering system - but it does change what "in" and "out" mean. Many levels involved with the focuser do that also - sgp, the ascom driver, and the hardware itself will do this. But the numbering of the focus positions and the range never changes.
That's why going from high to low during the focus curve could lead to a conflict that can only be resolved by changing the motor wiring or something - which is what I did.
But if high to low happens to match the way your system should take the focus curve - it is all fine once you get the in/out and backlash set right.
Frank