Why is there no lift kit which utilizes a rear axle flip and an upper control arm T-bar attach? (Newly engineered upper control arms go down to T-bars, brackets attach below to hold lower control arms, steering system redesigned/augmented as necessary)

This type of design would give more suspension lift than otherwise possible and would keep ball joints and centerlink within spec.

You mean like Trailmasters 4" Toyota lift kits from the early 90's ?
The used brackets to basically lower the IFS away from the truck 4 inches.

The reason we don't have one is because the torsion bars mount to the lower control arms instead of the upper like on Toyotas. That would leave our torsion bars out in the open below the frame ready to be broken be a passing rock.

After reading your post again, it seems you want to move the upper control arm to the lower arm position, then lower the lower arm below that. Hmmm... that would be about a 10 inch lift.

Regardless, my answer is "No market for it" and "Too expensive". Designing any suspension kit that works costs a lot of money, and manufacturing the parts costs even more. Once you get over $2000 for an IFS lift kit it's pointless when a solid axle swap is a possibility.