This is a tough one!

I'm honestly not sure how to handle other fusions in the world of ancient centaurworld. Garnet is CRUCIAL to the plot and themes of SU so there's simply no way this au could exist without her, but her creation is already very peculiar (and accidental, aha).

I think. I would like to have other fusions exist in the world in the same way Garnet does! However, I don't know if they'll be made by OUR gems- perhaps there's a Rainbow Quartz equivalent made (through magic) by a different Pearl and Rose Quartz equivalent elsewhere in the world?

For example:

A random deertaur and horsetaur! Let's call them Cara and Renneigh (yes that's a horse pun no i'm not sorry)

Renneigh is, as a horse centaur, fairly privileged and is expected to to maintain an air of class and grace... which means not dilly dallying with the servants. However, there's a deertaur that she's particularly fond of, and they become friends and start hanging and even fall in love! Because of the Dragon Shaman's beliefs and the strictness with which they're maintained, this is Bad. Each kind of centaur should only be with their own kind. Yay for fantasy racism (sarcasm. SARCASM.)

Much like Rue and Saff, them interacting outside of working together (or, more accurately, one working for the other) is HIGHLY FORBIDDEN. And centaurworld.. well, its inhabitants frequently defy even its own expectations.

Cara and Renneigh's love for each other might spark a new life- something that in SU we would recognize as a fusion- but here would become a separate entity in mind AND body.

Their child would probably look similar to a child spawned by Pearla and Rosa's love, if they ever had one. I don't know if that's in the cards for them at the moment, honestly! Maybe in the future?

One thing's for certain, though, Rosa's herd is where outcasts (and their possible fusion children) tend to go, so if we see any more fusions, they'll be very nearby! Perhaps Cara and Renneigh made their way to our herd (the crystal gems) with their son, Ranibow. (that name is not a typo. yes he's named after the meme. i'm hilarious.)

Perhaps he's even a playmate or cousin-figure to our little Steben!

The mixing of two different species (whether by magic or more mundane means) always results in something not quite like either the parents, though! A deer and a horse, in this instance, made a rainbow antelope! Maybe Pearla and Rosa would make a pink and blue zebra? Maybe they would make a donkey? A goat?? It's hard to say! Even two children from the same two parents (using the same method) would/could result in wildly different offspring (unless they're made at the same time, in cases of twins?)