The weak arm is an issue, but it's more important to catch a ball than to keep a guy from advancing. How often will a guy be on first with no outs, and get to third on Revere when he wouldn't have gotten there on another player? One time a week, two? How often will those guys then score? IF his OBP were higher, he clearly has a great shot to be at least league average as an OFer in terms of offensive+defensive production. I don't get the whole "4th OFer means they are giving up on him or holding him back" thing at all. Play him 1 time a week in LF, one time a week in CF, pinch run and defensive substitute the games they are ahead, let him hit late in the game when they are way behind and likely won't come back.....there are plenty of ABs and defensive opportunities for him to continue to grow, even as a 4th OFer.
Besides, Benson is a few months away from being up on a regular basis, if he cuts down on his SO% at all. If not now, when, for Revere?