Hmm. something seems off on your first slide.
Went I input the all the original pick up points on my car using the OEM alignment specs, ride height in particular, I came out with an 8.25 roll center height. Snapshot of that below.
When I dropped the chassis down to my preferred ride height ( the lower control arms pivot points level) and pretty mild -.5* camber, I dropped the roll center down to 5.53". Slide below of where I'm at currently with a 26" tall tire.
This is using the stock E body disc spindles. I was originally thinking of swapping to FJM spindles for the additional height, but based on my previous experience, that would raise the roll center a few inches higher. I even got a bit excited about the prospect of these aftermarket spindles once you dug up the original manufacturer, just because it would be a nice option if everything stacks up correctly. However, without doing the work to see where my rear roll center falls, I'm reluctant to just swap the spindles. My thought being that the raised roll center height up front isn't necessarily good or bad, but without knowing what sort of moment arm it creates to the roll axis, I don't want to start experimenting until I can get the car off the jack stands, consistently running, and and turn some skid pads laps to create a baseline.
I'm also taking a bit of an unorthodox approach to being able to lower the car further; I'm raising the engine and trans mount somewhere between .5 to .625. The thought being that if I can get the oil pan and headers up outta the dirt, then I can drop the body of the car lower which is going to drop my inner pivot points for the lower control arms, creating new instant centers. But, its all just mental gymnastics right now. My first priority is getting the dang thing running again.
