Hi log1c,
marked your answer as solution, thanks a lot. I build it as suggested for one server with two instances and received errors, that my new hostname is not known (I assume this comes from agent, didn’t investigate any further so far, maybe this can even be solved), but I can run the tests via ssh for the additional hostname at least, so this is a way I can go.
Thanks for your idea! 
Regards,
Dirk