The best argument in favour of signing him is that he has earned it. He's not getting in out of pity (nor should he be left out of pity), his record at 14-1 is good enough to merit a fight in the UFC. The argument against it is (likely) bad PR.
Problem will be finding an opponent. Fighting Newell is the strongest case of a lose-lose situation i've ever seen in MMA. If you beat him, you won't get credit, if you lose, you're reputation always will entail losing to a guy with one arm.
UFC probably will push a low-level guy, who is afraid of getting cut and doesn't have any leverage, to take the fight imo. Only option.