This is how I generally try and position myself and I think more and more startups will find this type of role valuable, but as of now I don't see many startups that are explicitly looking for this type of early employee.
Where are you located? My company is currently working to improve our marketing, and it would help a lot to have someone who can both set marketing strategy and implement it, instead of just one or the other.
I think it's one of those roles startups don't know they need until it's a little too late.