Essentially, Paramount would have to re-open the entire post-production department to do this ... and basically re-cut the entire series. That's editors, foley artists, producers, visual effects artists, payroll, crafty, everything
The audio was totally adequate when it was was remixed to 5.1 surround for the 2002 DVD releases.
Only the visuals need to be upgraded.
librarians, film-to-tape telecine operator, assistant editors, picture editors, visual effects department [CBS Digital would do the work (same company as TOS-R)] creating CGI models, CGI animation, colorists for final picture 'grading'.