Hi Derek,
I didn't even know you could customize an ABZ, but I would say that ANY finish Sheldon does is top notch. His satin finishes are really nice, and his gloss ones are beautiful as well. My ABII has a figured bubinga top and a satin finish, and I wouldn't want it any other way.
As for the drop B string tuner, I've never had one. But Sheldon never does anything that isn't well engineered and tested first. So I would certainly not worry about the functionality aspect. Also, many have them and I've never heard anyone complain that they are somehow not all that.
Finally, be sure to head over to the Dingwall site (you probably already have) and ask Barry about these things. IN case you are not aware, there is an "Ask Barry" forum and his contact info is posted in there as well), He is extremely helpful and a really nice guy to boot.