Ge0rge: Surely "received at Post Shop, awaiting courier uplift" couldn't be that hard to implement?
If you're prepared to renegotiate international postal treaties, define new EDIFACT service codes to add "received at Post Shop, awaiting courier uplift", and convince every postal service on the planet to adopt them then no, it'll just be a small matter of programming.
Edited to add: I'm not sure if you'd need to renegotiate postal treaties since I'm not sure at which level enforcement would work, so just added that as a backstop.