I think a Welcome To Steem-Monsters Special that accounts 30 days or older can't play in would be a good idea. This will help new players get a footing in the game would be a great tool for affiliate to use to sign up new players.
Restricting players with higher level cards from playing in the lower level tournaments isn't a good idea. A person who paid for a Diamond deck did so to open up all possibilities of play. Why would they want to spend all that money just to limit themselves to one aspect of the game ? Bronze / Silver / Gold / Diamond all have different aspects to over come due to the different card stats in each. It makes no sense to restrict a portion of the game to ones who have unlocked all portions of it.
That being said, Another suggestion that is likely better then my Steem-Monsters Special suggestion above is turn the Novice games into the newbie learning league and lock them. Once your account upgrades a summoner pass the novice level you can no longer play in it. It can be advertised as the learning tournaments before entering the official competition, Bronze +. This should give any newbies a sufficient experience on what tournament game play is all about.
I have to respectfully disagree with you. The end goal here, which I think everyone can agree on, is for mass-adoption of the game. If newer players are continually belted by players that are eligible to play in significantly higher tournaments, then the game becomes no fun, they stop playing, they stop buying packs and they tell their friends it's shit.
I think there should be Completely open free for all tournaments that anyone can enter without a fee, from Novice to Champion, and you enter knowing that it is likely to attract a big crowd, prizes can run deep (and possibly have a chat feature for a bit of friendly banter during the tournament).
In addition to that, I think there should be restricted tournaments that are purely for players within certain brackets. The Big Guns don't have to be eligible to enter everything, just like the rookies don't have to be eligible to enter everything. The main aim is to make it fun and interesting for all levels of skill and investment, and a combination of free and paid entry tournaments at different levels, as well as open tournaments where level is irrelevant, in my opinion is the way to do it.
The top 20 players don't have to win everything
I can agree with the majority of that. There is room for all shorts of different variants of tournament play. I think where we differ is I think such games should be one off games and not staple games.
There is also little to no disadvantage to the ones in the smaller leagues when facing a diamond player in that smaller league as stats and game play are different in each league. The player with the advantage in such a situation is the player who more routinely plays in that specific league. Moving down can be just as hard as moving up is. The only outlier I see is the Novice league which will have the newest of the new players learning the basics in which I believe would be a good idea to turn into the Learning League.