In my opinion this is not a good idea because it would give Bridge Burners 18 subcategories. There isa already a 1P Multiple Controller subcategory for GamePad Island if you want to play a multiplayer category by yourself.

For that matter, why is there a restriction against single player using multiple controllers for the regular Bridge Builders run to begin with? If there's no requirement for footage of the players playing the game, then there is no way that a mod can definitively say that other people are NOT involved in the gameplay, so seems to me it would be easier to just allow for multiple controller use.