Doc's been doing this, to an extent, but rotation has a lot to do with what substitutions the opposing team makes, and you have to adjust accordingly. It would be nice if we could just have a steady rotation, to throw our subs at the other team in waves, as you suggest, (great idea, by the way - TP - you'll get no hammering from me), but there are a lot of other factors and variables involved, (like injuries, tempo, being a bit unpredictable to throw off the opponent), when actually implementing that rotation, and regularity is, unfortunately, not one of them.