Legacy League Party Play Mechanics

Heya folks, just a few questions on the upcoming Legacy League mechanics.

So far as I know we can only have 3 different leagues activated per area. How is this going to work when you party up with other players? Will everyone's leaguestones be active at the same time? Cause having 3 leaguestones active per player with a full party of 6 means having 18 leagues activated at once. How is this going to work when you can only have 3 different leagues active per area? Cause if all 18 leaguestones are active at once but you can only have 3 different leagues active per area that would mean most of the party members losing the charges on their leaguestones.

Anyone have any info, ideas or suggestions on this?

I can't remember a source so may be wrong, but IIRC only the instance creator's stones will apply.