YES! Another MUD programmer! I started writing one in Meteor about eleven years ago. I don't even know if Meteor's still a thing anymore... I've had a few projects in Rust that were mixtures of roguelike and MUD models, conceptually. I usually got aggravated with the models I created, though.

I really like your multiplayer idea. That sounds really clean and flexible.

IndexedDB seems really cool. Never really worked with it but seems like a good option for you.