Manage content for multiple websites and mobile apps

I need to manage content (pages, key/value list, assets and more) in one webbased system for multiple websites and mobile apps.

My idea is to create a web api, secured with tokens for apps and sites and some kind of OAuth authentication, also with JSON web tokens. I want to create it with ASP.net Web Api, Entity Framework and Identify.

My idea is to split up the cms into a single page application, probably in AngularJS, and the Web API. So first create the domain model, how do we need to structure all the content/data and store this. After that create the api. And when that is finished, I need to create a SPA-cms webapplication for the end users.

Every website or app can use the api to read and write data over https and with a secret token, and every other party is free to choose whatever technique or programming language they want to use.

What do you all think about this idea? Can it be a architechture/technique to use for a long time? And do you think this architecture can be used for high traffic websites?

Thanks!