First person to click the Waystone sees the normal menu, but anyone who clicks it while the first clicker's menu is open sees another option "Travel with -username-" then everyone who selects that teleports with.

Or it could be anyone within range of a stone, which could be interesting if animals, mobs, etc got transported too.

Sounds good to me if done for "anyone within range". Perhaps a consumable should be required? Eg: you need to have as many ender pearls as people/entities you're traveling with?

Hi, I created a PR for an implementation allowing players to take leashed animals with them when traveling.
I added multiple config options to keep it customizable, but I was not sure about what default values to use