Why not a percentage of the profits? That's what he's asking for, so obviously that's what's going to motivate him. Then he'd have the incentive to make the cold calls you want him to. As it stands now, there is no incentive for him to make cold calls, he draws salary regardless. Seems like a Win-Win situation to me. A lot of large, successful companies are doing just that.
if it ain't broke, don't fix it