The recents Treks are crap. So he can't make the franchise worse.
The recent Treks (movies & TV) are just crappy run-of-the-mill action flicks, rather than character driven. So Tarantino making a Pulp Trek or Kill Bill Trek really would not be new. About the only "new" thing he could add would be the n-word, a Ferengi Unchained perhaps.