For me keep the aspect ratio, and just trim down the epilogue and remove mentions of Bruce’s dreams.
Ah, finally a fellow 4:3 defender! These changes would definitely be my top priorities and for a conservative fanedit (that would please even hardcore fans) those would probably suffice.
I had also thought about splitting the film into two parts. Part one being around 2 hours and 12 minutes with the ending be the rescue mission and realizing they can bring back Superman and part two is everything else.