The perfect place for Thomas is coming off the bench. He's a perfect pace changer. Because of his size his defense will never be stellar. He also forces his offense when it's obviously not his night, sometimes to the detriment of the team.
Reggie Jackson has an upside remaining, he has normal size, his D can and will improve, his point guard skill will get better, and his scoring will become more efficient.
Thomas does have a team friendly contract going for him.