I share my US family plan with friends in the UK. Their account would be banned occasionally. So, Google is probably aware of this hack, it's just they are not enforcing it too seriously.

EDIT: they only banned the added family member, not the account owner. My workaround is to just recreate family member account.

I use a Thai account. It works but the Google account needs to have the country set to the same one used for billing.

So I’m going to slow down my gigabit symmetric internet and route my traffic through a third party to hypothetically save $5.00/month? Wouldn’t the VPN be more expensive?

You don't need a VPN. The account will work without one.

This is a TOS breach for sure. One day you'll find yourself banned from all Google properties. Is it worth a few monies per month?

It's a separate account but them banning all related accounts is definitely a risk.

I assume this would need to happen just once during signup?

For a normal subscription, I think so, though their entitlement seems very random.

But for a family plan you may have issues adding people to the plan. I couldn’t add my girlfriend to my US family plan in Mexico for example, and it eventually booted her because it didn’t think we live together.