I must admit i don’t understand what you want at all.
A widget button has nothing to do with the “onPressed” event of a gamepad button. An “onPressed” event from a gamepad is absolute. You can link that to an input action or directly catch the event from a blueprint like for example the level blueprint. You can put whatever logic you want behind that. It also doesn’t make sense to switch the actual mappings, why would you do that. Let’s say you switch up and down on a gamepad, it would just be hell of a confusing. Rather put your “move up” function on the “onPressed” event of the directional pad down button.
I’m pretty sure you could switch the mappings with C++ or by editing the UE4 source, but i still don’t get why.