Yeah that's nice and all, but for practical purposes it doesn't make a huge difference. As MikeT said, OPS is a better predictor of team runs scored than OBP and I don't feel like multiplying by 2 every time I read the stat. Generally speaking, we are talking about the difference between .350/.450 and .340/.500 or something like that where it doesn't really matter anyway. Use whatever run estimator you want, and you will very rarely find a guy with sub-70 power in the top-10 in the league in that category. I can just about guarantee you will find multiple guys in the top 10 with one of the other ratings (probably contact, but maybe vsL) below 70.
 
It's doubly redundant, because I say the guy with 70/90/70/70/70 will out-OBP the guy with 90/70/70/70/70 anyway.