Why would they have to go back to the models made for the '97 SE? Couldn’t they just use the new and improved models used in R1?
I’m sure the programs ILM uses have progressed enough that they couldn’t plug the new models into the 97 (likely made in 95) animations. So they’d probably have to start from scratch.
The original SE Jabba they made was animated manually frame-by-frame using stuff they built for Jurassic Park.
On the commentary track for Episode III, an ILM guy talks about how they weren’t sure the Boss Nass model created for TPM would work with their current software, (to their surprise, it did) and that was only about a six year gap. I would think a 20 year gap would be impossible in either direction.