I think Four-Ball format would be a great addition. Before AS, I believe WGTLS guild matches were manually scored as Four-Ball. And Four-Ball format was successfully used in the WGT Ryder/President's Cup tournaments, They played 9 hole matches.
Include a pick up your ball and a concede option to keep things moving along. It would be a popular addition to multi-player IMO. I can't recall the last 18 hole AS I've played but keep it an option.