When you say "get on" the new companion, I don't see that phrasing as something sexual, what I imagine is mounting her for a piggy back race, and it would be a companion piggy back race... We'd all be racing Doctor Who companions towards a red ribbon and a photo finish.
I'm certain that Katey Manning couldn't support my weight.
I'm amazed that the ponds didn't leave after the Doctor tricked Rory into killing one of his wives. That was the time to leave. The Nimon episode was just a blood bath, there's no way that wouldn't have rocked their faith in him since it was their faith that was the weapon being used against them.