Spotsjock, I do have to say that the interchanging hookers game plan does have its merits and allows for a fresh talent like Sullivan to carve up and spark the attack when the players are a little more tired. You do, however, have a point on using up replacements and we can easily counter that by putting Sullivan on, and slotting Bosnich to the back row or Lock.
Until Russell Aitken is ready, I'm actually a fan of Sullivan at 5/8th and believe he could have the same impact, with time, as Craig Wing. Wing had similar problems when he was young and making a name for himself.