Probably be just easier to assemble all of the developments in the past 30 years — the DataQue 65c816 upgrade,VBXE, dual POKEY, etc — into a “super XEGS”. But getting software developed for it is the big problem, as we’ve seen with VBXE.
The VBXE is non Atari. That's a huge argue to not support it , if you want to have software running on stock hardware
That "SUPER XE" studydesign conception? ... came 10 years too late, as it would have needed 3-5 years more to set a system to the real world.
Things would have been so little to change, to bring the Atari to the late 80s: Just changing the GTIA chip, allowing some additional sound channels (particular for bass sounds) , a dedicated memory for storing character data and moving objects.
In a "native mode" ANTIC could be used for DMA preparation and 1.79MHz (minus refresh cycles) had been available for calculations, as the Advanced "GTIA" would allow to turn ANTIC DMA OFF ...
The rest of the machine would have needed no changes.