Here are our basic requirements:
1) JSON API for pulling and saving types of content (images, text/markup, other assets)
2) Easy to use Dashboard for editors managing content
3) Ability to tag/label/organize content and have versions of content like pulling the phone version of the same piece of content.
4) Ability to set some logic/rules on content like passing in a variable and having a different version show for instance, A/B testing content
5) Bonus points if it has image processing features like upload a master image and it will convert and provide all the optimized versions for different devices/phones like cloudinary