The idea is simple: while in the main game map you'll able to host a player which will spawn in a random point of the game at least 2000m far from your current position.
Basically you can keep on playing the game as you would do in solo (except starting main quests) but with this new feature: the other player could be behind the corner and ready to kill you.
It's some sort of realistic bounty hunt. If the players fail to find each other within a certain time lapse, both players will receive a clue saying something like "the enemy player is somewhere in john's territory or in jacob's one". If the can't find each other they will keep on receive more clues which will be more and more precise than the previous ones.
It's a real hunt since you have (at the start) absolutely no clue at all on there the enemy player is.
In my idea during this mode player should have limited access shops, allowing you to buy only regular cars and weps and no choppers or gl or rl.
Personally I don't like FC5 multip at all. I think my idea would quite simply and fun: imagine you fighting a group of cultists and then suddenly out of nowhere, you see someone arriving on his car driving madly and opening fire on you so you must take cover and prepare for a serious fight!