Well since World's Finest is happening, what would be an interesting scene I'd like to see unfold would be this.
So both Superman & Batman are both on the trail for *insert villain here* and then they find out an assassination is going to occur at a ceremony involving various leaders of the United Nations, welcoming a new country which could spark an international incident and potentially WWIII and then make it there. Batman is then searching various rooms in the building and then something like this happens:
The DCAU JL/JLU fan in me wants to see it happen. Plus it'll be a great stand out moment for the new Batman. The rest of the scene then plays our naturally and the assassin tries to make a hit but of course Superman saves the day with his bulletproof body.