I disagree. The only thing that would take some time and money would be the ending, and even that is still achievable without an enormous budget.
Yes, TFF needs more work than TMP needed, but its still possible to let Shatner do his cut of the film for a reasonable price.
Well, being one of the few who like the movie, I can definitely tell you it's not because of the FX lol. If they wanted to bother and do a director's cut, they basically have to throw out 80% of the effect shots and redo them in higher quality and with better staging, as several posters mentioned before. Is it doable! yes. Will Paramount bother? I don't know.
TMP was a better liked movie than TFF. TMP also only needed minor touch ups (fix up the pacing, cut out too much unnecessary stuff, the actual scenes where new FX footage was rendered was probably 2-3mins worth of the movie, TFF would probably need at least 20mins of new renderings)