This system would encourage people to be toxic towards whoever is the weakest emotionally on their team.
Every time a mistake is made, or even if the game just looks difficult based on the draft, the people with fragile egos, who have difficulty coping with minor losses or discouragement (the toxic players) will start looking for a way out of receiving a loss. Your system opens an easy escape for them. All they have to do is to "convince" someone to leave.
Once someone starts that process, the game is lost. With one player actively trying to make the game as unpleasant as possible for someone, by trolling, flaming, feeding, pinging, emoting, or whatever else they can do, it will be very difficult to carry the game. So, once one player starts, everyone else on the team will become discouraged. Those other players will now also start looking for the weak link.
If one player seems immune to their pressure, they will switch focus to the next likely target, so even if you can handle blatant trolling, what are the odds that all the members on your team are firm enough to convince the fragile one that their tactics wont work AND they're able to do so quickly enough that your team still has a chance in the game?
With all the games that have any bump in them being swarmed by trolls, how quickly will the game cease to be enjoyable? Also, in all the games where you are able to do well, your opponents will fall apart, handing you the hollow victory. Participation trophies like that don't provide much enjoyment. It's much more fun to beat opponents who are trying their hardest.
That's a doom and gloom scenario, but if we inspect what happens with the current system, even the losses that occur don't have much impact at all.
In the player population X, there are Y players who leave.
Because the system is not designed to place leavers specifically in your games, on your team, (Why would they? How could they?) we are safe to assume that every slot (that is not you, because you don't leave) has the same probability of leaving.
There are 4 slots that are not you on your team, and 5 slots that are not you on your opponents' team.
The total number of leavers on average for your team is then 4Y/X. The total number of leavers for your opponents' team is 5Y/X.
We can simplify the ratio 4Y/X : 5Y/X. The X's and Y's cancel out. We are left with a ratio of 4:5.
You will win 25% more games because of AFKs on the other team than you lose because of AFKs on your team.
The current situation doesn't seem to have any downside, except that AFKs exist and those games aren't as fun.
The doom and gloom scenario would have more AFKs, and more trolling.
If you wanted ONLY to decrease AFKs, you would have to have a lever that only intersects with that. Perhaps just multiply their LP loss by 1.5, or something along those lines. Emergencies can happen about once every six months or so, and we don't want to overly punish people for those instances.
