Hey Sylvester,
the existing holes for three different heights of mounting the Z assembly already have some play and people spend more or less time for tramming the Z axis (=adjusting the Z axis for perpendicularity to machine bed), what has to be repeated every time after you moved the Z assembly to another height.
If you wanted to move this up and down easier (which I think is a great idea), you would have to find a technical solution that maintains the alignment of the Z axis perpendicular to the machine bed. This is quite challenging. In industrial machines, this is done so that the entire X-axis can be moved up and down, as seen here:
– Source: Kief, Hans B., Roschiwal, Helmut A., and Schwarz, Karsten: CNC-Handbuch, 31., überarbeitete Auflage 2020, Carl Hanser Verlag, München
They call it an additional “W” axis.
I am already thinking of making my own Z assembly for a longer time, a more universal assembly which would enable to attach a spindle like a Teknomotor or an Elte. What you would need is someone who can mill the parts out of aluminium. At the moment, I have not this capability here.