I also don't see a need to increase 5-ball potential players. They should be special and rare. 4-ball potential players I would personally like to see more of. And, I agree that more 3-ball potential players and higher 19 year old skills would make the draft a LOT more interesting.
But, I also think part of the reason that the TL is flooded with poorly trained perennial all-star and above players is because the teams that are able to draft them are on average the managers that are less active in the game. ie, the managers who finish in the bottom 6 in their division and have the first 6 picks in the draft. They're able to draft high-potential players, but then they don't adequately train them for whatever reason (lack of understanding of the game, lack of interest, inactivity, etc). By introducing a mechanism where teams who finish with an above-average records can still prioritize drafting a high-potential player, I think on average you'd see better trained players on the TL. I'm just talking averages, not every situation.