Have you thought about designing your knuckle to be 2" taller than stock from the centerline of the hub/spindle and drop the lower ball joint mounting location 1.5" to 2" from the centerline of the hub/spindle? Droping the ball joint mounting location would be the same as what Chris Birdson is doing with the lower ball joint drop brackets he is running on his B-bodies with a longer upper ball joint. I'm not entirely sure where he's ended up for upper ball joint length.
I looked at raising the hub an inch (1" drop) but the outer tie rod end looked to become a limiting factor on wheel depth. Part of the reason to go to an 18" wheel is so you can run a 9" or 10" rim and a decent offset to get the tire under the fender. 17" wheels run into that problem and are limited in offset to like +30mm on an 8" wheel, and dropping the ride height 1" would put the OTR in about the same spot and create the same limitation.
And I don't think a 19" wheel work on an A-Body as the front tire is about maxed out at 26" OD. That would make the sidewall shorter than I am interested in running.
I haven't put much thought into making the spindle taller, but not out of the question.
Also, my understanding is that an A-Body has pretty good geometry with the LCA horizontal and any slope down to the wheel make it worse. And with the LCA horizontal, the car is pretty low. So a 1" drop spindle would end up with the LCA sloping down at the same ride height and wouldn't be the best idea, in my opinion.
I could get behind a 14" rotor and 6 piston caliper. Have to keep that in mind.
I haven't heard good things about the 4 piston S550 setup. Vorshlag has nothing good to say about them, partly because of the way the venting is on the rotors but I didn't get the impression he liked the calipers either.
I need to get back on finishing the bracket design. It currently works with drum brake spindles but I would like to come up with a solution for the disc brake spindles.