I've since revised my approach yet again. The previous design I had (file too large to load) was proving to be cost prohibitive and too complex to manufacture in a reasonable amount of time. Despite being disassemblable, I have no good place to put the beams and several cross-members where they won't get damaged when not in use.
Since fixtures are only required for the front and rear subframes (powertrain location) I'm building a smaller 3'x5.5' table that when finished can be stowed in the corner of the shop and used for general fabrication.
It will consist of 8 8"x42"x1" steel plates spaced for T-clamps (similar to what you'd use on a mill table). These will rest on 3 2"x6"x.25" beams and each secured via 6 3/8" bolts. If I need to expand upon it, rectangular tubing can be placed across the table and fixtures placed upon them.
There are no permanent levelling jacks. This bench top will mount to a 1 ton scissors lift so it can be elevated and moved independent of the vehicle. 4 jacks can be bolted on when desired. The vehcile itself will be supported by 4 leveling jacks that can be fixed to the floor. This also helps when pulling the engine. Removal of the front clip allows the table to slide beneath and the powertrain unit can be dropped out easily.