I like the idea behind the suggestion, but honestly I´d prefer it not solved via the Potential (=Cap) Frontier but by some individual "development speed" factors (scoutable). I don´t really like the link between size and the training speed all too much (although I see some kind of link between some skills and size, but overall I think it´s silly), having a rather unique set of "what he might learn quick" and "what he may not learn fast" skills would be interesting. Shouldnt have too much of an impact though, more like factors between .85 and 1.15.
Zwei Dinge sind unendlich, die Dummheit und das All...