Yes, but chat teaming makes it likely for you to get backstabbed. Once someone would get a kill, someone would clean up, then someone would clean them up.
4 player deathmatches speed up the game too much. Most SG games last 15 minutes, and unless you want to bring that down to 10, 4 player deathmatch would be too quick. Besides, the people who camp at spawn will get more stacked than players going for chest routes, and that means the strategy of knowing the map is no longer the best way to win.
Refill would never happen with 4-man DM.
"More confusion" means that there are more people to keep track of. With 4 man DM, players spread out more. You are squeezed between two guys, and then there's another, so it makes sense. You would have to dodge arrows from one person, run away from a stacked player, and try not to make enemies with the last guy. That would be very difficult to process and avoid.
"A feel of greater intensity." I see where you are coming from, but fighting a team and worrying about the last guy sneaking up on you doesn't make "intense" sound like such a great thing.