while I like the concept, I do have to say one thing.
The defense originally had total control over the placement of players within the box. This led to "exploit blitzes". Eventually the higher ups said that they just couldn't code for every type of new exploit blitz and said screw it we are going to lock down how much you can move the guys in the box and thus have a smaller thing to code for.
If you allowed for this, you open the door for two things:
1) Widening the gap between good OCs and bad OCs. While this sounds like a good thing, here's the reality. Eventually blitzing would need to be improved in ways to allow for them to be effective against good OCs. What may have been a balanced interaction between a mediocre OC and a blitz, now becomes skewed in the defensive favor.
2) This would make it extremely hard to tell real exploit blitzes (where coding cannot pick up a defender), from just bad blocking assignments. We are still having issues with blocking assignments that are leading to near insta sacks being worked out, we don't need to make it more complicated just yet.