[Complicated] Would this constitute an OC?

So let’s say you have an AU where Rarity herself is the same as in canon more or less, but she has a previous incarnation where she was a sphinx.
 
This previous incarnation had a different name (in this case: Sekhmet), and a different but thematically parallel life story, but she intentionally looks a lot like Rarity species-swapped because, from the designer’s perspective, that’s exactly what she is. In the AU lore, Sekhmet and Rarity are synonymous, and today’s Rarity can spiritually link with her past self and physically transform back into Sekhmet.
 
Would this constitute oc:sekhmet, or should we tag rarity :: sphinx :: species swap :: etc.? Should all of these things be tagged together?

It’d be all of them. There’s some precedence for this, like Siden’s AU, though that didn’t include the race swap thing.