I was thinking of having the end of the shockleader right at the sinker clip. That way the swivel on the trace would slide freely up the shockleader and onto the mainline with nothing to go over except the shockleader knot.
The rubber band is only there to hold the trace straight while casting.
If a fish is hooked, the trace-swivel would just push the rubber band down to the sinker clip.

Tangles could well be an issue though

The other problem that might occur if using floats is the bait floating way up to the surface and snaring a gull..