I prefer the route Adywan has gone with ANH:R HD, in switching between AI upscale BD and UHD depending on the quality of the shot (with unifying color correction, of course). That’d be the best way to structure a Despecialized version, IMHO (along with print sources). Like take a look at this example:
It makes sense to upscale BD shots when the UHD equivalents get bad. Likewise, luma and details from the UHD can enhance the BD well enough.
I much prefer D+77 over this route you described that awyidwan did.