Doctor Who: 10 Things That Must Happen In Series 10
9. Bill Being A Belieavable, Consistent Character
Similarly, even Clara's biggest supporters have to admit that she had some jarring personality changes through her three season tenure on the show. One season she's a perky nanny grieving her mother's death, the next she's a fully-qualified teacher with serious control freak issues. Then, she becomes an adrenaline junkie with a death wish. Oh yeah, and now she's an immortal with her own time machine.
Though Jenna Coleman was awesome in the role, this sort of haphazard character development limited how much we could invest in Clara's journey and believe in her as a person. For Bill, then, it would be best if things could be scaled back and we could return to the days of the likes of Rose and Martha; an ordinary young woman who finds something extraordinary in herself when she travels with the Doctor.
The companion is meant to be the audience's identification figure, after all, and we can't identify with them if they aren't a belieavable, consistent character.