It would not be that hard to do...
I mean the ressource, by scalling the SOR4 landscape assets + perhaps AI assisted pixel conversion.
About the characters, it's the "hard" part, even if Blaze have a spriteset in some SOR2 edited version. (beside of the numerous variant of spritesets she have in these...)
Axel should not be so hard to do either... considering the size of SOR2/3 sprites...
Or just rip them as-is-where-is and drop them into a high resolution version - but that's not happening, and if it does you probably wouldn't like it. I certainly wouldn't because it would be another bad look for the engine. Creators with @Kratus level talent tend to be ethical enough to leave still living assets alone, and the kind of people who would just take stuff on day one - well, the less said about their quality, the better IMO.
DC