I agree that it would be good to have companions from a different era - they were much more common in the Classic series!
Starting with the doctor's grandaughter, Susan, with the first two doctors we had Vicki, Stephen, Sara Kingdom and Zoe from the earth's future, Katarina from the fall of Troy, Jamie from 18th century Scotland and Victoria from the 1860’s - so 8 non-contemporary-Earth companions, as against 5 'present-day' ones (Ian, Barbara, Dodo, Ben and Polly)
The third Doctor only had contemporary Earth companions, but then he was confined to contemporary Earth for most of the time!
The Fourth doctor had Leela who was descended from human settlers on another planet, Adric who was from ESpace and Nyssa who was from Traken as well as Time Lady Romana. The last two also travelled with the fifth doctor, as did Turlough, from the planet Trion.
The Sixth and Seventh doctors companions (Peri, Mel and Ace) all came from modern Earth, though he met Ace on another planet and it was never adequately explained where Mel came from.
The Eighth Doctor had several companions in the Expanded Whoniverse of novels and audio adventures, including the edwardian Charley
and the alien C'rizz, and some of them were mentioned in the prequel to the 50th special, giving them 'canonicity' (if that's even a word...)