The short answer is no. That said, if you have lounge access, an agent may make an exception for an MCE seat assignment (assuming traveling companion is not basic economy). Same could be said for a gate agent, however I would find that unlikely. As far as luggage, that is a hard no, but as an F pax, you get 3 free, so maybe check-in together and check their bag under yours? That would also be a reasonable time to make a request for an MCE seat for your companion.