I suspect there are several people in this forum that feel very strongly against the idea of SC publishing the details of their matchmaking algorithm, but please, hear me out.
An underlying reason why players are frustrated with matchmaking is because they don't understand how it works. Many match-ups are unfair or perceived as unfair, and it is not always clear how or why the two clans matched in the first place. I propose that units in the game (defenses, troops, heroes - anything that affects war weight) be given a war weight value that is posted whenever you open up the information button (little blue "i").
The values would be posted along side their other statistics, like damage, HP, etc, and would also show how much increase whenever you hit the upgrade button. On someone's profile, the offensive weight and defensive weight could be totaled and posted for all to see, along with the combined war weight. Finally, whenever you match another clan in war, you can see each clan's total weight, which would be a sum of the individual combined base weights (this is oversimplifying I am sure).
The reason I support this idea is because it would bring to light whether the individual unit weights make sense. The community could provide meaningful feedback on potential tweaks to weights based on their testing experiences, rather than guessing what the weights are and how they are calculated in the first place.
The main criticism I anticipate with this is that people think it will lead to further exploitation of the matchmaker. To this I say, we are beyond the point of exploitation being a limited problem that needs to be contained - the majority of clans out there are already engineering their bases to a certain extent in order to give their clan the best possible chance of victory. The underlying problem is the incorrect valuation done by the matchmaker, not the behavior of the players. You won't change the behavior of engineers, you can only make it unattractive for them to do so.
Finally, I think this idea came from a Clash with Ash video a long time ago when he actually did CoC videos (burn!), so I can't take credit for it. Additionally, I would argue that a change like this is essential for the long term stability and fairness of the MM system. There have been many great suggestions on the forums, and I will readily admit that I have not had time to read them all . However, I would welcome a discussion on this idea and links to parallel discussions if they are relevant. Thanks!