Would you like a spin-off show, "The Companions"?

The storylines for most of these characters are finished though.

Amy is dead after living her life in New York with Rory.

Donna cannot ever remember the Doctor or their adventures, or else she dies.

Rose is off in another dimension with her own version of the Doctor.

The next time River Song sees the Doctor has to be the library. She specifically says in Silence in the Library that the last night they had spent together was at Darillium. We've now seen their time at Darillium, so the next stop has to be the library for her.

Jenny (his cloned daughter) was a one-off character who will never return to the show in any form, and is probably dead now as she seemed to be pretty much human.

The only ones that might possibly work are Clara, Me, and Martha, but those are problematic. Clara's story is done and for even people that like her (as I do), it would be really odd and somewhat disappointing for her to come back to the show in any form. Her story has run its course and has ended beautifully. Martha is actually a possibility, seeing as she just left of her own free will and nothing catastrophic happened to end her story. However, considering how long she has been gone and that the Doctor has lived for 1000 years since he knew her, it would be odd for her to come back now.

Me, on the other hand, would be about the only one that would make sense seeing as she is immortal. The Doctor could now run into her at any point during her lifetime both before and after her travels with Clara. It could always be written that after a few (or many) adventures, Clara decided it was time to return to Gallifrey and be sent back to trap street, and Ashildr could then steal their TARDIS and run off to encounter the Doctor. This is also a way that Ashildr could make a return and become a companion (which I would love) once Maise Williams is done with Game of Thrones.

/r/gallifrey Thread