I think it's a good idea
Well, if you are to have a list of trustworthy services, it's an added bonus if there is a list of services that are scam where people who try to do extra research can look to. It would also help identify services that were previously legitimate and have gone defunct or have turned into scam
I'm thinking of using color codes like this:
I am more in favour of the option "if the mixer is not on this list, then it is unreliable". It is too much work to find all the fake, phishig, scam sites, and it is never possible to list them all. There is always a new one.
Such a list must have a log on the regularity of updates so that the reader can be sure that he has fresh information.