Thanks again for all the replies, folks! I saw that Topeak rack that bored117 mentioned on their website, and was intrigued, but I needed a disc-specific rack and I went with Topeak's Super Tourist DX Tubular Rack w/disc mounts rack instead.

That Street Cuff looks pretty cool, too!

As far as mounting my massive u-lock I opted for the Abus bracket that I alluded to in my original post. It turned out to be an elegant, yet practical solution. I ordered the bracket and some new Ergon grips from Wiggle in the UK. It was my first time ordering from them and I was quite pleased with their prices and service. They offer some things (like the Abus bracket) which I just can't find locally or through North American online distributors.

In any case I have put many winter commuting kilometres on my ride since I got the bracket and the lock has stayed secure and out of the way through them all. I will post some pics when I get a study break.