If Ratatouille mechanics were real, there would be a whole market of businesses offering the services of operating rats to people who want them, and it'd be like how bees produce honey. People in the rat business would be so exhausted of having to explain over and over again that no, the rats aren't being exploited. If the rats didn't like how they're being treated, they would simply not return. There's no goddamn way to force a rat to be so passionate about playing the saxophone that they'll figure out how to puppeteer a human to do it for them. All that the business does is finding a way to put that specific rat in the hair of someone who's about to go on stage.