I think it is a good idea to make sure that people don’t have too much trouble finding opponents to play. That is both in the interests of some players individually but it is also in our collective interest. If some players, and especially new players, have difficulty finding opponents, than we will have trouble keeping people in the league and getting new people to join.
I don’t think mismatched games are necessarily a problem. It may be less interesting for the better players but it is a good learning experience for newer players and helps them become more competitive in the long run.
At the same time, I don’t want to add to the work of those who manage the league. So I would support an ELO system if it can be implemented in a way that doesn’t add to Gamerman’s work.
If that is too complicated, another option is just to score tier 3 the same way as tier 2. M and some E ranked players would still lose score in those games, but they would lose less, and everyone else would still go up.
Also, its worth noting, with new players at least, that losses to E and M players increase their average. There is a very good chance that players who start out at tier 3 will end up at tier 1 or 2 by the end of the year, and the more losses they have to E and M ranked players the more likely that is. So there is less of a disincentive than might appear at first.