Thanks for the answer DSA. I should have said this was for a game engine.
Animators don't like new things
I was basically thinking the hybrid FK/IK spine with stretch would be what I would go for, but good to see others agree.
By the way DSA do you know of any particular rigs with a spine like that that you like? Or any tutorials you like? There are tons of tuts and examples online but sorting between them is the tricky bit.