OK, I thought that if devices could be limited to a stat or rank, then implementing the different flavours of voodoo would be a straightforward question of working out a desired rarity and how powerful to make the devices.
I guess that it would be possible to simply strip voodoo powers from the regular gals and implement voodoo gals as separate entities, but that might take it too far.
Unless it could be disguised.
When the player makes out the order on the black market for, say, 20 gals, can the game randomly roll for each gal and, if lucky, replace her with a voodoo gal? If the gal looks and acts exactly like a regular gal until the power is unlocked, the behind-the-scenes-maths would remain hidden and the player would assume he was just lucky.
Devices can be made that only work on some units, right?