I look forward to coding a site using such an API-based CMS sometime. Never really had much exposure to such a thing, although it makes sense.
Currently, I specialize in Joomla. But, whether you’re a Joomla, WP, or Drupal CMS developer (the big 3 in open-source), you still find yourself in the same boat of building on (or installing) additional “CMSs” atop those CMSs. I’m speaking of things like ecommerce cart software, for example… Each add-on product like that basically adds what amounts to another CMS atop whatever you’re extending. So, sure, we have off-the-shelf products to handle most things that clients want. But, when it comes to truly custom software or systems that manage client data and integrate w/ their main CMS, we usually still have to build out our own mini-CMS atop (or aside) the main CMS. Hope that makes sense…
At least with Joomla, it’s fairly easy to leverage Joomla’s own framework to make those add-ons work well (e.g., database and user classes). In this way, we can indeed fairly easily (well, for tech people) build out any additional / custom data needs we have, yet still leverage the safety of such a large open-source framework.
Anyway, great read. :-)