Personally, I'd condense the death into the first 20 minutes (a lot of that is just action sequences and splash pages anyway) and make the last 40 minutes Funeral for a Friend and AoS #500, wrapping with cameos of the 4 Supermen. I think having Superman save Henshaw is probably more important than the Justice League getting involved.
Part 2 would probably spend about 20 minutes cutting between the Supermen. At the 20 minute mark, we get Henshaw's heel turn. We see the Supermen pair off in fights. Eradicator vs. Steel. Then Superboy vs. Cyborg. Cue Superman's return. Final 20 minutes: Assault on Coast City.
Might be tempting to tease Emerald Twilight at the end. That could spin naturally into a Kyle Rayner movie. Then "Morrison JLA with Kyle as the POV character" as a series of movies, one per arc. Then a pair of Rebirth movies for Hal and Barry. In the background setup passage of time so you can get around to Jon.
