If you apply a water soluble coating to the copper, you shouldn't need to modify your laser printer to be able to print directly on the copper (except perhaps to compensate for the thickness of the board).
We sell such at coating at www.laserpcb.com, and I thought I'd "open source" the recipe for everyone.
1 cup water 1 cup isopropyl alchohol 4 tablespoons Carbomer 940