Let me share my own thoughts on the current format.The number 1 problem is lack of stability.
Clan League turned into a scheduled yearly event and it works out great. NC should follow the example and be held in the window between CLs, something like from July/August to November/early December.
Problem is, you need to find someone to organise it. And that's the same problem like, for example, finding community moderators. People who really want to do it are usually the least competent, while the unbiased and pragmatic people usually have better things to spend their life on.
We will see around May 2024 if someone capable comes up, or maybe I will consider organising it again.
And honestly this number 1 problem is the only real problem in my eyes.
Your format suggestion is good.
But like you noticed, it takes 8 rounds to find the winner, and that's with only 24 teams participating. But we always have 30-40 teams playing.
If we could have 8 or 9 rounds, it'd be easy to come up with a better format than what we have now. I myself have a bunch of ideas in my head. The challenge is to find a format within our time constraints. Or maybe people wouldnt have a problem playing 8 rounds? I don't know, it's up for discussion. But from my experience, people start getting bored around turn 3 already, unless they are the very top team that believes they can win it.
the absence of any elimination round that makes it possible to become the winning team without having played against the runner-up team
Is this true? Well it was true in 2021, but if set up correctly, there's only 1 team with perfect score in the end. If the final round is ClearFavourite vs Underdog, it's because the Underdog team must have beaten some very strong teams early on.
matchup randomness within teammates (the best player can be wasted against the weakest players of the opponent team and lead to a different result)
I think that this pinch of randomness adds some fun, or at least it's not objectively a flaw.
Your solution with player hierarchy adds a bit of additional work both to the event organiser and to individual team organisers as well. And I don't think people want this.
We both like MDL elo ratings so let me show you something.
Every team has an option to drop the 6th player and have their best duo play an extra game, at a small cost of -1 game point.
Is this a good idea?
Mathematically, if you estimate your worst player to win 25% of his games, and your best duo to win at least 50% against same opponents, it pays to drop the weak link.
In elo world, that's the difference of 200 elo. If your worst player lags more than 200 elo behind your best duo, you should consider dropping him.
There are a lot of teams in this situation and exactly noone ever does it.
To me it's strong evidence that people aren't that much interested in team management. They just want to find 6 guys and play.