Have it to where people on your friends list could come in to the game. (host has to invite them) have a list of open games that the players could message the host asking to join, if the host agrees (and trusts them) they can invite them. in the end when one of the players leave, the host gets to choose what they get to keep (or they could talk it over and trade objects for each other via voice chat.) the character coming into the game will have whatever they have in their inventory, nothing else. All events will play toward the host players game. (mini encounters, houses, missions etc.) The players will have a set distance they can travel from each other before they are forced to come to one of the players (players Choice) Each account will have a set number of characters they can create. the player coming into the game will take the place of the host's follower.
if anyone has any further questions, thoughts, and or comments
or if you have a specific situation that you can think of that may happen ill do my best to answer.
-Thug