Having watched the two really good combos of Superman 3 and 4, I've been thinking that it would be a REALLY good idea to make Superman 2 the last part of a major trilogy, placing the majority of events of 3/4 in the middle...
1) The story should have a narrative structure that incorporates Lex Luthor, following his numerous captures/arrests/escapes...
2) Superman's love for Lois should only be cemented AFTER he goes back to Smallville and explores his relationship with Lana...
3) The story should end with Superman choosing to be the hero and Lois having her memories intact, but realizing his role is greater than their love (for a bittersweet ending)...
4) Keep the narrative away from the Richard Lester slapstick, but don't use the incomplete "test footage" for a more accurate "Donner vision."
I've been playing with this narrative structure in my head for quite a while now, and I may attempt it eventually myself, but I'm nowhere near the Faneditor that some of the greats around here truly have become.