You suggestion actually turns me off on the game a bit. So it would not get me to add another team at all. I feel like 2 teams is a good amount for me. Only thing that would get me to add one would be:
1) Cheaper
(I know you said don't say this, but its true).
2) More quality worlds.
(I am in Happy Jack right now that had an almost immediate roll over, I like that. I am also in Addicted Users, which will probably have a month long recruiting process because little effort goes into recruiting before the World Series Starts, I don't like that).
3) Coach hiring change
(I hate this aspect of the game. Bidding on coaches AND free agents at the same time in a lot of bidding at once. There are strategies on both than just rub me the wrong way, particularly with coach hiring.)
4) Spring Training
(I dislike this too, too long, and too many line/up moves. No one I know of has "competition" for spots. This should all occur in 1 day and just be like a "Practice Minutes" thing in other dynasty games. Where you can improve / maintain stats based on practice minutes.)
If these things were fixed, along with some fix on advanced scouting... I would consider adding a team, because the game would be more streamlined and fun for me.