I've always thought that it would be right to ensure that best players on the team take more points than the worst when you win, and lose less points when you lose. The system already does this by comparing your MMR (affected by kills per minute) with your CSR (affected by win/loss). That's why a team of 4 who play all 10 placement matches together don't place exactly the same unless they all hit the upper limit of Diamond 3.
In this way four players of the same team who play n ° games together, rise or fall at different speeds in the ranks and the carrying up / down is limited.
given that I do not know perfectly how the MMR system works but, If this were the only parameter, I would find it strange because I could continually throw myself into the fray to make more kills, at the cost of making as many deaths and penalizing the team. Equally strange that a player with 15 kills and 20 deaths would have a higher KPM than one with 10 kills and 5 deaths.
I would find it more correct to evaluate KD or KDA, which generally rewards those who do not expose themselves too much and play in a more reasoned way. Or, in objective games, the position at the end of the game.