I don't think he filmed enough footage to make a worthwhile director's cut, unfortunately. A lot of the stuff he wanted to do never went before cameras.
The summer of 1989 was a very exciting time to be a teenage movie buff. In addition to all those, we also had Karate Kid III, The Abyss, Licence to Kill, Weekend at Bernies, Turner & Hooch, Parenthood, Uncle Buck, Friday the 13th VIII, and Nightmare on Elm Street 5 all opening in close...
In Shatner's defense, the film's budget was whittled down bit by bit while it was in development and production. It's not like Paramount told him up front that his movie wouldn't have access to ILM or half the other resources Nimoy had gotten on the last two. (And if they had, there's no way...