Don't food warmers have too high a minimum temp? Seems like you would want to keep food temps pretty high to avoid health issues.
Your objection is sensible. One should look for one with a suitable temperature range. That should be fine for colour. For B&W I would just adjust development temperature, but I have no idea what temperature paper developer needs because I don't print. I gave for granted that colour paper needed high temperature but that might not be the case.