I agree that the tires are too tucked in as well. I am going to purchase some new rims (18" AT Italia'*) and am going to carefully measure the wheel well/hub dimensions to see if I can get a slightly different offset to flush them a bit better.
I agree that sticking you're low-rider gold-spokes 6" out the side is a bad idea, but something less drastic should be alright. I'm not sure if it will improve handling because it actually depends on where the contact patch is moved in response to the suspension that'* trying to keep it on the road, move it too far out and you'll get weird forces on the joints (like the Polar Bear says). anyway, I forget the actual math involved, but most aftermarket wheel are available in several offsets.
And we aren't "adding" an offset. All rims have an offset, the Bonnevilles stock wheels are ? (gotta go couldn't find it, hopefully someone will fill this in), it'* the distance from the hub to the wheels centerline, by using a lesser offset, we can push the outside of the tire under the fenderline, as we pull the hub face into the center of the wheel.
this link will help calculate changes in clearances