I agree that having specific cat clinic times would be great for putting yourselves out there as a very cat-friendly practice and encouraging cat owners to bring their animals along.
I also think that cats are more likely than dogs to get stressed at the vets, as much because they hate car journeys and being contained in a carrier as anything else. I'm not sure it's the case that cats get more stressed if dogs are present in the waiting room. Cats can get just as stressed in the presence of strange cats as they do with dogs.
Tbh I'm not bothered by my cats sharing a waiting room with dogs, but I suppose that's because my two cats share their lives with three dogs. I can certainly understand why other cat owners would prefer not to have dogs around at the vets though, if they thought it would be extra stressful for their pets.
I'd also like to think that if my cat needed a vet's attention urgently that I could get the next available appointment rather than have to wait for a cat clinic. I like to be able to get an early evening appointment, as I work full time.
In short, I think cat-only clinics are a good idea, but that they probably will benefit the owners more than the cats. However, as owners are the ones making the appointments, this is very relevant.