Unpopular opinion: Although many people in FH want horse models, I feel like it would be a nuisance to have in-game. Horses are not carnivores (or omnivores) and wouldn't really work in a game based around everyone's favorite furry predators.
There are a number of horse-based games, but none very much like Feral Heart simply because horses don't really.. work, in my opinion.
Canines and felines are relatively similar in terms of size, anatomy, and amount of customization; a horse most likely wouldn't provide as many options, seeing as they are - in very general terms - all anatomically the same (coming from someone who lives with a horse enthusiast).
I know some people agree with me but not many, so I'm just putting this out there although someone can probably explain it better than I.