Since the diamond only mixes passivley, it's best to have as many individual colors as possible.
Does V2 allow me to add 12 extruders and only mirror extruder 7-12 to 1-6, since I only print with one diamond at a time?
Then depending on which diamond hotend to use, set enable signal of 1-6 to high and 7-12 to low. Steps and dir still get send to all 12 extruders.
(some minimum extra hardware need to control the enable signals)