Here’s a potential timeline for the opening act to a three hour cut
Reveal message
-Open the movie with Lois in mourning, fetching her coffe, visiting Clark’s memorial, segues into Diana’s mission to thwart the bombing.
-Steppenwolf seizes the first Motherbox, Amazons discussing sending the arrow to Diana, but we don’t need to see it shot and land or Diana discovering the all too convenient shrine to Darksied. She relays all necessary information to Bruce later.
-Bruce dreams of Knightmare Superman only, wakes up, and is visited by Martian Manhunter, who offers to help, this provides better motivation for why he helps Lois out as ‘Martha’ later, doing his own small part, and it also enables Bruce to become more aware that an invasion is immanent rather than the gut feeling he has.
-End the prologue with Diana and Bruce discussing Darksied and Diana asking where the others are
-Begin Chapter One: “Don’t Count on It Batman”