Your needs are such that buying gift cards with cash is not secure/anonymous enough for you, yet it is too painful to use open-source software from outside the App Store?
I would suggest that this may be too small of a market to be commercially viable.
You may be right about open-source software being sufficient on Apple gear. But I wouldn't want to go through the hassle of buying gear anonymously, and then discover that I need something via Apple.
I'm sure that I represent a small market. But it's arguably a market that Apple must serve well for Tim Cook's claims about privacy to be credible.
I don't see how buying gift cards for cash in person is less secure than buying something online for bitcoin. Cash would seem the least identifying and/or trackable way of purchasing gift cards.
One can easily use VPN services and Tor to anonymize IP address. And one can easily anonymize Bitcoins using various mixing services via Tor. But in buying gift cards with cash, there is in-store video. There's also cellphone tracking, for those who are careless.
But I do see https://giftoff.com/gift-cards/apple-store for buying Apple Store gift cards with Bitcoins.
I'll give it a go.
Edit: It seems legitimate: https://bitcointalk.org/index.php?topic=970780.0