1) I dunno about the Delanos, but the FD-3's are very bright and "honest" sounding pickups to me. I'm particularly fond of the P-Tone.
2) Yes, many times. My best results have been with M/N taper pots, and I like 500k to keep things bright.
3) No, but I've routed additional pickup holes in my Dingwall (that was just as scary as it sounds) and installed an FD-3...
4) Now you're talking crazy...
Basically, the electronics on Dingwall basses are GREAT and represent an important part of the sonic recipe.
With that said, although they don't need modification, the underlying tone is so pure that they are a great foundation for more elaborate electronic schemes.