I could see a gift card being an okay solution if it were instead, say, redeemable private currencies I could redeem for a currency of my choice, but I was thinking more along the lines of something I could use at any legitimate merchant, but not a fencer, illegal gun salesman, or street-corner drug salesman.
What you are seeking is the current credit/debit card system with reversible transactions an no anonymity. Such as system currently does not allow payments to individual private persons. I normally can't meet with a person that I find on craigslist selling an item I want and pay him with my debit card.
When I was thinking about this, I was envisioning a rubber hose kind of scenario, where bitcoins were being demanded of me, but it would be impossible for me to send them to the thief, so threats to make me hand money over to him would be ineffective since I couldn't send money to his address. I could give him the physical wallet hardware and password, but then he'd have to only use it at registered merchants, where the blacklisting and unblinding, as you mention, would come into play.
You shouldn't be carrying devices that have access private keys to large amounts of bitcoin, so they can be coerced from you. The average person doesn't carry large amounts of cash so it minimizes the risk. The risk vs. reward ratio should be large enough to deter most criminals. If you are uncomfortable with carrying around a certain amount of cash, you should also be uncomfortable with carrying around the private keys to the same amount of bitcoin.
I would really prefer that no amount could be easily coerced from me, and I've never mentioned reversibility, which this scheme would not enable. Fungibility isn't really limited since the limits can be easily reversed once you arrive home.
