Is Joomla a viable alternative here?
If you don't mind relying on 3rd party contrib modules and external development roadmaps, you can build apps in Drupal, but if you just want a framework to build and deploy your own web apps Joomla is fully extensible in the OOP sense.
Also Joomla is classier than Drupal. :-P
I didn't play around with it long enough to remember anything about its file or database architecture. But, I think if I were going to develop a CMS, I would want to make it easy to patch and upgrade, and I would want to make sure that it was somewhat secure.