Serve static files through a custom handler or register in app.yaml?
Use the static handler:

You don't need to startup an instance to serve your file.  This generally means it'll be served quicker, and you save on CPU hours.
You don't have to worry edge caching.

The cons might be that the files are static, and it might require more manual intervention with your framework.
In a project I'm developing I'm using several Python projects as dependencies. These projects each come with static files (JavaScript, images, etc.) and a set of handlers (with default URLs). To register the URLs for the handlers I add them to the routes in the WSGI application. The static files however need to be registered in the app.yaml. This is something I would like to avoid so it becomes a breeze to register both handler URLs and static files.
I thought about implementing a request handler that takes a file location and serves it with HTTP cache (like I think the default static handlers do).
I've discussed the idea with a colleague and he thought this was a bad idea. He told me that when registering the static files in the app.yaml the files are served in a more optimized way (possibly without Python).
Before I go and implement a static handler I'd like to hear what would be the pros/cons of both methods and if the static handler idea is a good idea.
In current projects we let Buildout generate the app.yaml from a template. The static files are added there. The (obvious) downside is that this process is error prone (if done automatically) or redundant (if done manually).