in reality, ur right, Kobe never gets be Kobe unless he is in the NBA, MJ never gets to be MJ unless he is int he NBA etc etc.
So in real life, this is positively true.
so i like ur idea where the is a 'floating potential' that may be influenced by the level which they play at.
But perhaps it should punish lower league trainers. I dont tihnk a potential should 'drop' as such, thats unfair.
instead maybe - all players, regardless of the division they are in can reach say, 80% of their potential. Then, the higher division they are in, the closer to 100% of their potential that can be reached.
it could be another factor which allows teams to push a player to be better. so yer. good one :)