I'm looking at the Hidden Side sets, and they all have instructions to build some of their minifigs in 2 different configurations. As far as I can tell, only the regular config is set as a minifig. The ghost variants are not.
For example in 70432 Haunted Fairgrounds, Ghost Terry Top doesn't have a named fig, and the 4 parts unique to the ghost variant are just listed as being part of the set, not as part of a fig.
Is this something that's OK to create? See image for Terry's isntructions