Mark Webber would be an excellent choice... he's critical of the industry, he's responsible, has a good rapport with people and he's more than capable of keeping CE in his place as an enthusiastic but biased car enthusiast- the programme then needs balance from someone who would provide at least some credibility towards the journalistic format. CE will always have the stigma of being a bit of a prat at times.
Susie Perry [?], with her 'Gadget' presenter's hat on, would be good as she has never looked comfortable in the BBC F1 link role.