LOL first-person=shooter mode? Like Overwatch or TeamFortress ? I think that would be awesome!

It's called Battleborn, and it's bad and dumb, and you're bad and dumb if you like it

Riot would need to set up an entirely new team to work on that kind of game because it is incredibly different than league of legends is. The market is already pretty saturated on strategy shooters because there is OW, battleborn, rainbow 6, and many more. It would be a poor business decision to start working on one IMO.

But if one existed, I would totally play the shit out of it.

Nah bad idea. If they were to make a LoL adaptation it'd be better to do it in an x-com/divinity isometric tbs style.