I can understand the thinking behind this and might somewhat agree, however i don't think they will. It's not financially benefiting them unless you want to count potential loss because people play blowout games causing them to leave.
Reason being, if they cut down significantly on the number of available teams and re-institute a waiting list you will have people who want to buy a team, and cannot for potentially 2 months (or more depending on how many people get into the list). So you have people willing to pay the flex, who cannot spend it or people who would potentially buy flex in order to buy a team not doing so because they won't get one.
A waiting list also does not mean that teams will be bought by quality owners. You will still get people who really have no clue what they are doing ending up with teams that are half filled or have no idea how to run a team etc. And potentially good owners might change their minds if they end up being told- nope sorry you signed up 3 spots too late, you can't have a team this season. This could cascade down as well since that might also mean a whole batch of new players not being made because some friends/group wanted to build together and now can't do so and they don't bother spending the money to make players.
Last issue is- If you restrict leagues down to the point where you have almost no overflow leagues (like the 6th league in a 6 league level) you leave little room for existing teams to make up for player loss along the way, unless teams start gutting, in which case that causes money issues since those teams are no longer being paid for each season.
Without teams to have excess players, people without a team (other than D league) will have no where to go. It's not very interesting to watch your player on a D league team. And thus those people will either not learn from other people, or get bored and leave, which cuts down on the pool of players and again affects the player/team ratio
With the current structure of age based leagues all feeding into a giant pool at the end, there is little chance you can implement this and have any significant effect on competition, player/team ratios or other issues within this area.
To sum up: This likely won't change, and the implementation in our current league system won't sustain it well for the reasons noted above. I wouldn't be bothered if it were implemented but i don't think it will be beneficial to the GLB system overall.
So can't give it a +1 or -1, just a 0. Consider my points, if they're not clear (went back a few times to add things so might be a bit jumbled) just ask.