My suggestion would change the game and help new users immensely. And yes, long-term managers would eventually face more competition. If they are as talented as you've been with your team then they will rise to the top as well.
However, if you just want to keep the status quo because it benefits your team and other long term managers the most, that's fine. Just don't expect everyone to agree with you.
The game will continue to hollow out and the number of new users sticking around will keep dropping because the mechanics of the game are broken.
And have been for some time.