Fusion is a hard thing to work with.
If anything, there would NOT be 2 people that come out of the fusion, and it sure as well would not last for 5-7 min.
My thoughts on this are as follows:
You must find the porunga ear rings on the map, then toss one to someone else (only sayjins can fuse). You stay fused for 2 minutes. You get a massive upsurge in power, health and speed. While fused, one person controls for 1 min while the other watches, then the other person controls for 1 min, then they un-fuse. At the end of the fusion, the purunga ear rings dissapear. Only one fusion per map. After the fuse, you keep the PL you obtained from killing people, but your life gets dropped to 20. This would be for balance purposes. It would give someone else the chance to kill you and gain a massive PL.
Even still, I'm not sure how the fusion process would look in the game.