V3 Purist edition is great!
Its near Perfekt. Only thing that comes to my mind that could enhance it even more, would be Rotoscoping the DVD effects into the HD Picture, but thats a bit “Too much” of work i think.
I still would love to see Trek 6 in the Long Version in HD. Always loved the ending with the Assassin Klingon beeing a Starfleet officer in Disguise.