Anyone that brings a knife to an airport at this point pretty much needs to be standing next to someone with an "I'm with stupid" t-shirt. Unless they forgot.

I still think they should have a mailbox with a vending machine that sells $3.00 priority mailers, so anything important could be mailed home.

Now that's an excellent idea. Japanese airports already have such facilities for shipping almost anything to your final destination. Saved my back on the last trip, enabling me to ship a lot of heavy stuff to the other end of Japan, and enjoy my in between time without schlepping a lot of gifts.