I'm an Amtrak engineer, too, Mr. Silverliner... I may not run on the high-speed Corridor, and I don't know anything about the AEM7, but I do have an understanding about how push-pull works.
I am also all too familiar with the behavior of blended brake while operating in push mode. The question I meant to posit in my previous post was - how do you design a cab car such that everything it does - including operation of the independent brake and the actuating feature - behaves exactly as if the engine were leading instead? Sure, it's theoretically possible, but the way current equipment is designed, it isn't.
Any passenger engineer with any common sense will bail the independent, when necessary, for better train handling. That's assuming that you're running from the engine. Like I said before, there isn't really any reason to bail the independent on a cab car (if equipped) if you can help it. It will just cause undesired slack action between the cab car and the rest of the train.
No matter what kind of engine you're running, isn't it usually best (while power-braking) to bail off only the first service, and then let the BC build up on subsequent sets? I realize that cab signal drops require immediate movement of the ABV to Suppression, without having the option of doing a split reduction, so keeping the engine brakes bailed off makes sense in that case. But why would you keep the BC bailed off for station stops? All you're doing then is diminishing your braking effort. You certainly know that engine brakes are quite a bit more powerful than car brakes, so if you want to be able to stop more quickly, why not let the engine brakes build up after the first service?
Most of us - myself included - tend to forget that PUSH mode implies that the slack should be bunched most of the time, while PULL mode implies that it should be stretched. Even today I still have my fair share of rough starts in push mode. Controlling the slack requires a lot more forethought when the power source is someplace other than where you are physically sitting. Not only is it difficult to shift the mindset, but there's also the fact that engines behave differently than cars. The brake cylinder pressure on the trailing engine responds (almost) directly to changes in brake pipe pressure. The cars, on the other hand, allow you to "piss the air away" much more easily.