There are a few companies that exist to provide exactly that service, which kind of look like temp agencies. Gitlab uses CXC Global in my country, for example.

I work for a company in the bay area that has about 1/4 of our employees as remote now, and 5 years ago had none. A PEO like SOI/Trinet is what makes this possible

That becomes the contractor's problem unless you live in the few places where Gitlab has a legal presence.

It looks like you can choose to be employee, https://about.gitlab.com/handbook/contracts/

I don't see anything in there about a choice to be an employee. Which makes sense, you can't employ people in a country without being an employer.

Correct, see https://about.gitlab.com/handbook/people-operations/global-c... and specifically https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/dat... for a list of countries in which we can hire you as an employee.

Do you just use 0.411 for countries where you have no COL data?