Core team can make or break a startup, hence forming the core team out of remote employees is not recommended due to the trust issues involved. That said, remote teams are picking up its phase due to the obvious advantages mentioned by you.

There is a need gap for a service which can resolve the trust issues, validation, equity, payments on both sides for creating a remote team for launching a startup.

Also, another major friction is the different employee/labour regulations in each country. The service should be able to take care of these regulations and compliances for the startups for seamless recruiting irrespective of the country, the potential employee is from.

But remote teams can at best be functional only for IT startups, especially ones developing softwares and up to some extent few hardware startups like those involving IoT due to the logistics constraints. So, in order to expand the domain of employment for remote teams; the service needs to take care of the logistics as well.