I think that physical/mental/technique could be a factor in basically everything a player does as well as why it goes wrong. I don't think there's any (or at least there's very few) "mental only" or "physical only" ratings since most everything on the field requires both mind and body (both strength and technique/speed/agility).
I think you'd need multiple growth ratings (Technique, Power, Intelligence) which would indeed be interesting - or just take the potential mechanic we have and put it on EVERY rating like in HC. Some ratings would almost always be close to potential (like SPD) while other may...or may not have a lot of room to grow (like AWR or RBF).
It would simulate the same idea and differentiate players on technique/intelligence when comparing similar physical traits while still allowing for higher chances for a 90+ SPD/ACC WR to be more successful than a 80 SPD/ACC WR.
To me, what you describe is less "potential" than a chances of success. 90s give higher chances than 80s but both could really be suckers and not NFL material. The difference is more that the 80 has less forgiving "mechanics" (i.e. he has to do more non-physical things very very right), and I think that could be represented with individual potential ratings.
To the person who mention Production - the only problem with that rating is that it only reflects what's been done lately. The reason that's a problem is system. If a guy is a West Coast mediocre-armed QB and is used in a vertical push it down the field passing game - yeah, he'll probably suck, but if I use my WC scheme, he'll shine. However, he PRO will be low and it will make him look worse than he is. Likewise if I have that QB, he'll thrive and then I can pawn him off on the CPU for waaaaay too much. Then again, I guess that's realistic too