One solution ( and its probably not the cleanest) - is to great a single layout that you can reuse in any game you make in the future.
Create 4 events to handle the pressing of the start button for each game pad
if gamepad 0 presses start - call function "spawn player" "0"
player.owner = 0
if gamepad 1 presses start - call function "spawn player " "1"
player.owner = 1
Then create a series of events to check which button was pressed for each controller
if gamepad button is down (Gamepad = 0), button = A) -> Call another function called "Shoot", "0"
etc, and do this for every button combination.
Once you set this up once, all you have to do is create events for each new game you create that has a function that matches the button press function call from your "input" layout.
so. on function "shoot" "0"
pick player.owner = function.param(0) -> do whatever should happen here
if you did on function "shoot" "1" it would do the shoot event for player 1 instead
I hope this all makes sense, im pretty tired right now.
But basically you only need to setup on layout with a series of if statements to handle each gamepad and button. Have them call a generic function EG: jump, shoot etc. And pass the gamepad index number as a parameter, so that you only need to have one function per button, which will determine which player to do the action to based on the gamepad index that initiated it.
once you set it all up once, you can simply import that layout to your next game, and include it in your main event sheet, and it will be all ready to go.