Based on everybody's good opinion of this upgrade, I did the rear brakes on my 95 Disco this way and it was remarkably easy. I talked with ZacK at RN and he hooked me up with all the necessary parts in a nice kit that was a great deal. I went with the Proline 110 rotors and calipers but Genuine pads at his recommendation and replaced the inner hub seals and repacked the bearings like a good boy.
Considering there are something like over 30 bolts to get all the parts off, everything came off nicely. Even the ABS sensors popped out with minimal effort. All in all, it was much better than expected and totally worth the effort to upgrade the rear design. I had a lot of trouble with the original style getting an aftermarket pad to stay in place, but this solves that quite handily.
While I don't notice a huge improvement in braking, it does feel a bit more solid. Maybe because everything's new? I have no idea. The only wrinkle I had was the Proline calipers were a bit close to the top edge of the rotor (vertical not horizontal - not a spacer/spacing issue) so it was rubbing. A little work with a grinder deepened the channel on the front end of the caliper, and it was good to go. It made a very slight chafing noise for a few weeks (I probably needed to take off just a hair more of the caliper) but everything's happy now after several months.
If you're doing the rears on a Disco 1, it makes total sense to go this route. Thanks for making it a discussion - it really helped me make it happen. And thanks to Zack for the advice over the phone and sending along all the stuff needed!