Efficiency aside, I think trying to switch to an air/air setup would be very difficult just in terms of parts and fabrication. Air/air is usually easy with a turbo because the turbo itself isn't anywhere near the intake manifold, and the charge has to be piped around anyway (so you just pipe it through an intercooler on the front). With the supercharger mounted the way it is on the LSJ, I honestly can't imagine an easy way to plumb it all away to an intercooler, then back into the manifold.
Besides, like I said, the early prognosis seems to be that the stock setup does reasonably well. If that's not your bottleneck, why mess with it?