I think it would work better if the rats were younger when introduced to the kitten as well because they would see it as more of a normal thing maybe? Even when supervised it could potentially get pretty ugly very fast however as you said people do make it work without any hiccups! I have a cat and my rats still get on with their lives but I do wish I knew how scared one would have been, I do regret that part. It would probably be less of an issue if your kitty was upstairs like mine. I guess it’s a personal choice and depends on what you’re willing to risk, it would suck if you ended up having to give away the kitty. Rats don’t live that long so personally I would wait it out. To each their own, I’m definitely not an expert, hope someone can give you safe and useful tips and good luck!