Then the feds find the guy you sold to when they try to sell them on Coinbase. And that person knows your e-mail, number, what you look like. You had to get the coins to them somehow.

Actually, that is kinda scary. The bitcoin I just got for selling a shirt could be one transaction away from child pornography. And it is all in a pubic database.

I'm assuming someone looking to launder a large quantity of BTC wouldn't spend it all on individually purchased shirts. But who knows.

And now that person knows exactly who you are.

Is there a big enough cash market for it to be worth "criminal enterprise" level money?

I'm not sure what you're defining as "big enough" here, but localbitcoins.com shows verified, well-reviewed people in my smallish city that would be willing to do up to $30KUSD in one transaction.

If they don’t require an ID card from their cash receiver.

The kind of people you're transacting Bitcoin for cash with definitely don't want to check ID, just the opposite. They likely don't want you to know who they are either.