how do you mean?
aftermarket vented discs will be the same dimensions (20mm width i think) so oyu've still got the problem of how to get a 20mm disc into a 0mm slot on the non vented caliper

if you fit a front disc set up to the rears (like some people do) then you would have to get a custom bracket made up to bolt to the rear end so that you could bolt the front calipers to it etc etc