Instead of having a custom Z Axis assembly for each type and size spindle.
How about developing a universal Z Axis with a flat mounting plate that would allow for custom brackets to be designed and used with any spindle you would like to try and mount.
This approach would also seem to fit in very nicely with the new customized machine ordering model.
Sort of like this example image…
Obviously the above image is just an example and the design would need to be prettied up to be in line with Onefinity’s sexy machine style.