The only flaw I can see in this thinking would be if there are caps on how high a player's skill can go in a certain area if they are a lower potential. For example if you could only train JS to a certain strength if your player was a 6th man even though he was below the salary "cap". I do not know if such a thing exists.
Excellent question.
A perusal of the transfer list suggests that there are no skill-by-skill caps. Just search the transfer market for any combination of one high individual skill and low potential, and you'll find matches. For example there are 3 guys with "wondrous" or better jump shot and "6th man" or worse potential. Clearly these guys have only been trained in one area, but their low potential was not a hindrance to attaining a very high rating in 1 or 2 areas.
What I do think -- and I have no evidence of this, but it makes sense -- is that it gets harder to train a skill the higher you go. A player might have a potential that translates to 6 bumps. But it takes more training to get 6 bumps in one area than 2 bumps in 3 areas. It takes more training to go from "respectable" to "tremendous" than it does to go from respectable to proficient three times.
That's just my opinion. I could be wrong.