Fantastic idea!! I've been working off and on with local 4-8 player games, but I had only been using the Javascript gamepad API. I like how you're using smart phones, this seems like a good way to go about it!

It would be nice to be able to mix game pads and smart phones -- when gaming with kids, none of my kids have smart phones yet, so it would be nice to be able to let them use Switch controllers if we have those on hand, or use phones if we don't.

Regardless, I'm interested in this, and would be interested in contributing a game or two. This seems excellent!