I guess, an alternative to actually fully axing DII and DIII would be to make them separate games. As a new player, you pick what division you want to play, and then coach in that division. So, if you wanted to start in DI, you could, and then work your way up from a D prestige team as desired. Or, if you wanted to play DII or DIII, you could do that, and the players available to recruit in each would be limited to the players currently generated for those divisions.
Separating the divisions like this would improve game play in each of them, I think.
That being said, if you didn't have to play your way through DII and DIII to get to DI, not sure how many folks would be interested, but that's fine. You could have fewer DII and DIII worlds for those who do.