localizing an app

CI does not really disallow anything. So in answer, Yes. The beauty of PHP and CI is that neither the language nor the framework tell you how you have to do things. But the framework is an MVC framework, but what you have described is somewhat confusing and sounds very much like a big fat controller. I would revisit your requirements or your plan, or you are going to find it will become an enormous PITA for maintenance and development.

CI offers libraries, models, helpers, controllers, views and hooks that can operate pre system, pre controller, post controller (and many more positions) which means your code can be DRY, portable, partitioned, testable and easily extensible as well as database independent.

Give CI a go, you will not be disappointed.

Paul.