I think this would be possible, but then again it would also mean you the employee would have to setup your own company to be able to work remotely for another one, and although the UG cost only 1 euro to start, you need to set aside 25% of yearly earnings until obtaining the base 25k for ensuring your newly founded company (GmbH). So this means a lot of hastle for what? The remote companies would need to offer serious perks to get people to jump through all these loops.