I'd have replaced the Klingons with the Romulans. Soran could easily have been making trilithium doomsday torpedoes for them in exchange for the versions he needed, and we'd have probably got both Tomalak featuring and a fight between the Enterprise-D and a D'deridex-class warbird too. Also, I wouldn't have destroyed the Enterprise-D, I'd still have had her become badly damaged in the fight at the end, where she'd "limp" home segueing into the next film. One thing I liked about many of the TOS films is that they take place either right after the previous one, or are relatively close to one another. So it would have been the badly damaged Enterprise-D that faces the Borg, and eventually succumbs to her "wounds" towards the end of the second film.