To be fair, 3S is one of the best fighting games ever made and still actively played in tournaments. A good Mister core would really shake up and revitalize the community, it would actually make a big impact.
We have SF3 Online which is an OK port (music is really bad though) but stuck on X360 and PS3.
So a CPS3 core would go beyond just game preservation, it would greatly support an active tournament scene.
edit
Just checked and there is a 30th Anniversary Collection on Steam and it has 3S. No idea how accurate it is...