I'm building a framework (this is a vast simplification -- please don't recommend using an existing framework instead, that's not helpful) into which I would like to be able to integrate other libraries.
The PSR-0 recommendation suggests that all files within each sub-namespace be contained within their own specific directory. To keep things less complex for users of my framework, I would like to keep everything in one namespace, but organize the files into directories.
If PHP libraries can register their own autoloaders with spl_register_autoload(), then why is it essential that this directory structure be adhered to? Is it feasible/permissable to simply eschew PSR-0, use my own autoloader for my classes, and then use (for example) Symfony's autoloader for any Symfony classes that I may make use of?