I'm not a big fan of this for the reasons which correspond to the original points as follows:
1. I'm not as much of a fan of coaching D1 in HD, so to me, making an "only D1" world wouldn't be a good move no matter what it's used for.
2. I assume by "won a title" you mean a national title. Well, I haven't won any of those (though I've come close several times). Why should that exclude me from participation in a world which includes other coaches who happened to win one more game than I have (the title game)? I see no reason to make this the qualifying standard.
3. This standard seems a bit more fair, but punishes people who play the game on a casual basis or don't spend as much money on HD as others.
Other than that, I like playing against a mix of opponents myself, both human and sim. I like that better than a world of all humans, so I'd probably not want to play in this type of world if it were full as you mentioned.