ICalling the Captain 'Jim' on the bridge is inappropriate. IMO.
Well, I do remember that Spock and Scott both called Kirk "Jim" a few times over the years but that was usually in at least semi-private (WNMHGB, Amok Time), or high-stress situations (Mirror, Mirror). There were probably other examples I'm forgetting at the moment, but the business of calling him "Jim" on the bridge is basically a McCoy thing... and we all know what a stickler for protocol he is. But Kirk never seemed to mind, so why should we?