3. Buyer buys an Amazon gift card at a physical store using cash.
I am not sure how this can be enforced. If a buyer wishing to commit fraud were to purchase AGCs via stolen credit cards (or other fraudulent means) to be used with this transaction, then #7 would involve the seller being caught on camera picking up cash-like items that were effectively purchased via fraudulent means. The fake name used in #5 might lead Amazon and/or Law Enforcement to believe the seller intended to launder money via stolen credit cards (or other fraudulent means).
Although the transaction would likely be anonymous if the gift card was purchased via legitimate means, if a gift card purchased via fraudulent means is used in the transaction, then Law Enforcement might figure out who the seller is, and the transaction would likely be frowned upon (due to the gift cards being purchased via fraudulent means).
6. Buyer uses his gift card to send something money-like to the Seller's Amazon Locker. For example, physical gift cards or gold could be used.
The Amazon merchant could ship a roll of quarters instead of gold coins. This would generally be unlikely, although if the buyer was conspiring with the merchant, then the seller would be at risk. Step 5 might make complaining to Amazon complicated, especially if they ask you to sign an affidavit that what was ordered was not what was received.
I believe that purse mitigates this risk by forcing the seller chose the exact items.
8. [...]. Theoretically, Sellerbuyer could intercept the delivery before Buyerseller gets there, but this seems pretty difficult since the Locker is likely to be far from Seller.
A buyer who wishes to commit fraud could potentially target a seller who is local to him.
A wish list on the part of the seller would probably resolve this issue, although I am not sure if wish lists are compatible with shipping to an Amazon locker. If you assume that Amazon lockers can be used with wish lists, then the seller would create a wish list, then the buyer would purchase items on the wish list; the buyer could prove that the item was delivered with the order history of his amazon account (I think).
With gold coins it looks like it'd be about 18% overhead, which is pretty bad, though still often better than the localbitcoins spread.
I would be happy to buy BTC from a seller looking for privacy this way. Since I do not have an active need to buy BTC anonymously, I would want the seller to cover all of the overhead costs, and I would want to get to buy the BTC at a discount (based on the amount of cash I need to use to purchase the gift cards) to compensate me for my time. I believe that it would be likely that one party to each transaction would likely be in a similar situation.