It would be convenient to have another character tester on hand, and you could be a good fit, but I have some concerns.
My main concern with you being a character tester is that you can be a bit temperamental at times, and I think you acknowledged this, somewhat, by saying that you, “have not been the kindest person.” Sometimes your criticism of people publicly was unprofessional, or attacked them rather than how they played, or really didn’t help them grow at all, and this type of behavior in a character test setting would reflect poorly on you, me, and the server as well. Character testing is a large undertaking, and certain moods or opinions on kits, players, character testing, or the server cannot affect a player’s score. Certain players may be hard to work with, resistant to criticism, have annoying kits, or other quirks that make character testing less desirable, but these biases cannot affect the character testing environment. There are plenty of kits or players I dislike outside of the character test, but I have to put this aside and judge them based on their performance in application to my criteria, which would be your responsibility as well.
I think that if the standards I set are upheld, it would be a pretty good idea, but you need to acknowledge what I’ve said here and make a good case/promise that these things won’t happen.