You run into lots of challenges doing this. Particularly, modern calipers have pistons on both sides of the rotor: the wheel spokes are fairly close to the stock "floating" single piston caliper and you don't have enough clearance for double sided calipers.
As I recall, all the bike's I've seen with updated brakes (floating disks and multipiston calipers) use the entire front end of a donor bike, or at least the wheel/disk assembly. Cast or comstar type wheels are pretty much required, the original wheel's spokes are too wide at the caliper location.