I think most people agree that something needs to be done with the Thursday slot for games, whether that's an additional league game by speeding up the season or in the form of re-shaping the National Tournament, change is needed.
I have to say the idea you've proposed, in my opinion, is the best one I've seen yet. I'm a traditionalist, I like the slowness of BuzzerBeater so I'm not a huge fan of the speeding up the server side of things, but I do think this gives teams, both elite and down in the lower leagues, something more to play for. As you've stated, changes should be easy to implement due to the format being used for B3 and the consolation tournament.
In addition to the pros you've listed, it also creates a chance for teams to earn more money if the winner is rewarded in each round of the round robin fixtures.