Works in theory if you're trying to whittle down a large group of prospects, but I think there are too many intricacies to use this as an effective method to evaluate individual players. For example (obviously an extreme here), you'd have a player with 5 JS/5 JR/16 OD show up with the same number of primary points as a 9/6/12 player when the latter would be more effective. You don't wind up purchasing all too many players, so you might be best figure on what build you're looking for and go from there, rather than trying the shotgun approach to get 1 player that adds up to 75 skill points, or whatever.
Excellent point. I'm be more cautious in judging all players by these standards.
Also, depending on what I run tactically, a positions main skills could differ especially if my players are playing defense on a different position.
This formula may need some fine tuning but I think it might suffice as a first check.