Don't the Abacks block inside on some plays? Midline?
Yes, they do on midline. But, on the goal line and short yardage, it's often too crowded to run a real midline play. There's not enough time and room for it to develop. Usually we're not running triple option either. We're running either QB follow (definitely our bread and butter short goal line play), QB sneak if it's a foot away, some sort of BB give (dive or belly), or a rocket toss. All of these are extremely quick hitting and none involve a read. And, we've been REALLY successful with this goal line package. I think the reason we're successful is because it is very much a continuance of our regular offense. Our OL are firing out low and hard just like they've been doing every other play. All of our guys are blocking like they have been every other play. Most other teams are doing a different package with a lot different methods than their norm. It also helps that they still have to defend from sideline to sideline with the inside stuff paired with the rocket toss.
Back to your point, I do think a big package could help with the midline, but not with what we normally do on the goal line. It's still an interesting thought though. I remember CPJ running a power-I on the goal line in our first 2 games of '09, we got killed on it vs Clemson and we haven't seen it since. Really, there's no reason to change what we're currently doing ... it's working.
I could see it being more of a possibility in short yardage (not goal line) out in the field where there's still some room to maneuver and everyone's not all stacked up at the LOS. There midline is still a possibility.