Minimal role where he heroically sacrifices himself in the opening sequence is perhaps the best thing to hope for at this point. Hal's chances of having a lead role or a co-lead role in a live-action GL movie again died in 2011 with the character living on borrowed time ever since as far as prominence is concerned. Once they started portraying him as a joke in outside media it was obvious they would go from turning him into an incompetent character to eventually stop promoting him altogether and kicking him to the curb and that's what happened. If Geoff Johns was still involved I imagine he might have tried to protect him in some way to at least have a good role where he isn't deliberately sabotaged or reduced so he won't feel like a threat to anybody else, but this is where we are now. The "Lethal Weapon in space" originated from Johns' time as the so-called "head of DC films", but the rumors about WB planning to kill Hal off or turn him into a villain also started while Johns was still there, so he would've likely not made much of a difference anyway.