I really want to see a epic battle to the death with Fliqpy and Lumpy. Some wanted Splendid and while that could happen, Lumpy is Fliqpy's arch-nemesis.
How it would play out
I think it should have Lumpy as a police officer. Fliqpy was doing the usual murdering but then Lumpy came to arrest him. I think it could play out as the episode A Vicious Cycle but Lumpy actually put up a fight, how he usually does. I think the fight itself should be like how Neamo did his Disco Bear vs Fliqpy. Though I think it should be comical and be like how Fliqpy fought his good counterpart.
Who I think would win
I think Lumpy would win. While Fliqpy has killed Lumpy, Lumpy killed or just stopped him more times. Lumpy could have the comical luck and random smart to win this battle.