I've got through loads of ball joints too.
Problems going to a Kingpin axle:
It's narrower, you'd have to get new tubes pressed in to really do it correctly. Also, in stock form it's really tight on the short side tube to install the coil bucket and control arms. I've seen it done on 2nd gen trucks and the bucket got in real close to the inner C.
Also, if you read the 1st gen forums you will see alot of people with issues running kingpins. I con't recall exactly what they were though.
Lastly, you have the ABS sensor issue. You'd have to figure out a way to fix that.
It seems the 2nd gen trucks had better luck with balljoints and the knucles/ hubs are really close. I wonder if you could replace the inner C's w/ 2nd gen stuff, run the 2nd gen parts out from there and still keep the ABS signal.