I have made several games with controllers, even a few with more controllers ... but I always had to make separate events.
You could have some groups with player actions/functions/controls disabled, and have an event for each controller which activates them.
if gamepad.0 A is pressed activate group X
if gamepad.1 A is pressed activate group Y
if gamepad.0 A is pressed, set players to 1
if gamepad.1 A is pressed, set players to 2
and use the players value as a trigger for the loops for actions/functions etc.