More variety doesn't just mean more good players. Some players wouldn't perform as well as they do now.
No matter how the game works, some owners are going to be better than others. Not sure what point you're trying to make.
Right now, some ratings are much more important than others. I think most of the bad trades involve a P with a high OVR and low CNT. Oftern with high VEL. If a new owner is thinking MLB, they can expect to get an OK to good P if they see those ratings. In HBD, unless the other ratings are very high, they're getting crap.
Same for very good eye, very good power, poor contact, and OK vR/vL. In MLB, those guys have a roll. Walk 100+ times a season. K over 100+ times. Hit a bunch of HR. Lower than average BA. No such player in HBD. Players with those ratings barely hit .200, maybe with 20 HR, and don't walk all that much. Another big advantage for some owners.
I also find it hard to believe there is such a human that can throw well enough to get out ML hitters, but they can only throw 10 pitches a day and then can't do it again for 4-5 days. Lots of those in HBD.
If it's a MLB simulation, it should try to model MLB. I think more player diversity would make it a better game. Just an opinion.