I'd say it's possible to play LoL with one hand now.

I do, I have 6 buttons on my mouse for all 6 abilities. Items are on my keyboard, but I could just not build actives

I'm pretty sure someone played Riven with just mouse clicks only and also a controller. but you're titles' not wrong. It's just that it was already known and they facepalmed.

Just play Vayne. All you really need to do is kite with right click 99% of the time.

I have a 12-key on my mouse in addition to a few other buttons/the mouse wheel.

I actually do play LoL with one hand for the most part. Occasionally I'll use my left hand if i'm trying to queue up actions extra fast.