A beautiful piece of work -
I did something similar but ditched the magnets as they were not accurate enough and had too many holes to drill accurately(No CNC ). With advice and help from Robert Brown ,AKA FocuserPro, I switched to light detection resistors(LDR's), led's(2) and only 6 holes(on a 5 filter wheel 1 row of 5 ,1 row of 1 for "home" ). The software auto seeks home and then auto seeks the number of filter wheels on power up - allowing for 3 to 9 filter wheels to be used.
Nothing as beautifully made as your set up - good luck and clear skies.