The ability to join a public PVE or PVP game and bring your character and base progression with you. If there was a map like Navezgane that had designated spawn locations for people to load their base and character in and out of. Being able to team up with randoms to take on a point of interest, trade, show off items and base building progress and then being able to leave that game and go to another while bringing all your progress would be awesome and could change the whole dynamic of the game. I have a lot of ideas to add but want to keep this short and leave it open for discussion.