If one wanted to add more monsters/creatures to the OT, you could take stop-motion creatures from classic Harryhausen monster movies. Not much more then a cameo, but it’d add some atmosphere.
Turn CGI backgrounds from the SEs into matte paintings using the same technique I used to make Coruscant look like a classic style matte painting (which I plan to do with the entire trilogy). This way you could keep the Cloud City windows and not have them be CGI.
Ambitious. Make to make some of the CGI creatures in the SEs look like stop-motion, like the Dewbacks for example. Would probably involve sharpening the textures and changing the frame-rate. The effects look so primitive I think with some tweaks you could convince a viewer that it’s stop-motion.