Have you seen this cryptocurrency usecase?

Seems to me like people investing in crypto wouldn’t be the same people needing to put things on “layaway” to buy them.

Maybe the better use case is having a semi-secured credit card backed by crypto and as long as you have your crypto locked, you don’t pay interests on late fees on purchases. That allows the user to buy stuff right away, not need to spend the crypto and avoid interest payments.

Trouble there is finding a currency that will pay enough to cover the interest rates a CC commands.

You could use a smart contract on the Tezos blockchain to do it easily enough.

Might not be smart -- volatility cuts both ways and things don't always go up...

why tezos and not eth?

Eth costs 40 bucks per transaction, tezos costs something like ten cents.

sounds like a cool idea. surely worth researching further.