Hey try this Smoken...before you grill the sandwhich, take thick slices of brisket and lay them on the grill for a few seconds each side. Talk about grilled steak flavor! Then make your sandwhiches. I tried your technique and that was the only thing different I did and wow what great sandwhich. I think you are on to something there.
You could probably do this also on a sandwhich press or paninini maker too.
Preston D