Realistically, what problem would you be trying to solve, anyway? Most of your braking effort is up front because that's where most of the mass is, including _all_ the drivetrain. The back wheels are pretty much only there to support the back-seat passengers, all the junk in the trunk, and keep the bumper from dragging on the ground.

With rear discs installed, you'd need to reproportion your braking force, but IMHO you'd need to scale it way back to prevent near-constant lockup at the slightest touch; your ABS would be working overtime. This reminds me of the old GM X-bodies with the poorly-proportioned systems that always locked the rear wheels too soon. I remember stopping at a red light in the rain, and watching a Pontiac Phoenix slide right by me on the right, and do a nice pirouette right in the middle of the intersection. Fortunately nobody hit him!

-- Andy