
Being a new guy, and having never replied to anything before, I don't know how much help I can be with this, but I think this is an excellent idea.
Getting out maneuvered and out flanked on the battlefield is a very real and very realistic threat. Troops just aren't of much use without bullets to shoot, gasoline to burn, and food to eat. So the idea of incorporating supply lines would really step up the realism of the game and add some more depth to it.
It would also be important not to go overboard with it. Troops still have fight in them after being surrounded by the enemy and receiving no supplies. It would be more akin to denying a plant water. It would be fine for a bit, and then slowly wither and eventually die.
If you wanted to get crazy with it, you could even make actual supply lines, and make supply depots (in the same manner one makes bases and seaports). A limitation of the blitzkrieg is out running your own supplies, so adding that in will also add another element of realism to. You could even go further than that if you wanted, but personally I think the above mentioned would be far enough to capture the real feel for the logistical side of things.
Just one man's opinion...