Bad news on the slotted wheel idea. A disk platter just laughs at a
dremel tool. Henc offered to cut the slots on his CnC machine and I
may take him up on it. He says he has a 2mm cutter and a disk platter
is 95mm in diameter (298.3 circumference) so the lands for 72 slots
will be just a tad wider than the slots. (2.14mm)

That should work.