Ppl over react about players attitudes sometimes JR is a little out there and not the smartest player but besides that brawl he never had any real team issues with Denver. He was always willing to come off the bench in favor of an inferior player in Dante Jones and Aron Aflallo so I don't think he'll mind doing this with Fields.
When the bench is struggling to score you have a guy that can go off for 30 on any night to lean on. You can never have enough fire power especially if you wanna beat Miami and Chicago, a matter a fact imagine Miami bench trying to contain Baron Davis, JR Smith, and Shumpert they'd have fits.
Like i said earlier, i 'm not a JR fan, but i'll give him a shot and see what happens.