How does MMR work in this proposed system?

- If your MMR is bound to teams and resets upon entering a new team, people will keep making new teams to smurf at low rating.

- If your MMR does not reset, people can leave their main team to intentionally drop MMR in another team, and I do not see how this can be distinguished from simply playing legitimately with weaker partners or team comps.

I do like the idea of making it easier to play with different people a lot, but I do not see how the proposed system will not be abused. As others have already pointed out and the only solution I can see, is to adopt the solo queue system (with the limitation that you can only queue as a full team).
It seems these valid and important points have not been addressed yet.