Leonardo.ai have basically done exactly this and seem to be doing OK.

It’s a shame because they’re literally just using stable diffusion for all their tech but built a nicer front end and incorporated control net. No-where else has done this.

Controlnet / instantID etc are the really killer things about SD and make it way more powerful than Midjourney, but they aren’t even available via the stability API. They just don’t seem to care.