Working with the excellent fbs tool (great stuff Michael!).
The manual has this suggestion about project structure:
As your application grows in complexity, you will likely want to split its source code across multiple files. In this case, it is recommend that you place them all inside one package.
My tendency is to use subdirectories like 'view','controller','model','service', etc wherein multiple .py files exist. Is there a critical reason one wouldn't want to use subdirectories when using fbs?