Crew Sizes or Custom Lobby

Recently it’s come to my attention that multiple people I game with (over 4, which is the max size for a crew.) Would like to be in the same game as I, and would like to either create an alliance or have more players (we thought up to 8) max crew size for the Galleon. Would this be something do-able? Even if the crew sizes can’t or won’t be increased, could private matches / lobbies be created?