Can a transfer be done over postal mail?
A1B1: Assuming you've prepared in advance, there are some nice offline wallet options.
A1B2: This one's tricky. I'm going to assume that you have access to a computer before running off into the woods, or what have you. I'm also going to assume that you know exactly the amount and address in advance.   


Generate the transaction and sign it, but don't broadcast it (can be done with Bitcoin Armory)
Print out the transaction
When you want to make the transaction, mail the transaction to your agent.

A2B?: Easiest one. Just write down your private key and describe the transaction.
A3B?: Well, you're screwed, because the agent could just never make the transaction.