My understanding is that there is a range of outcomes for each potential. So a Superstar could cap closer to a perennial allstar or an MVP. There's no real way of knowing until you train them
There is a youtube video on this :
(https://www.youtube.com/watch?v=tx8MB1qudRc)It may also depend on which position he plays. Passing is a high cost skill for a PG, but it's a medium cost skill for a SG. You might look at drafting a short Center (6'2" or shorter) and training him.
I have a Superstar player with 16JS, 9JR, 20OD, 20HA, 21DR, 8PA. Not the build you are looking for, but I would think it is possible.
My advice would be to scour the transfer market for 18 year olds at the start of next season. Set thresholds for the skills you want to train - you don't want any of those skills to start at 1. Buy 3 or 4 and train 1v1 forwards for a year. See where they stand after that
Might be a good idea to secure coaches now. Youth trainers are easier to buy than the regular ones. But you're less likely to get in a bidding war now.