What if we use a different file extension for EWL CSS files, e.g. .ewlcss? We could then have our CSS handler only operate on files with that extension. This would allow us to continue requiring the correct timestamp in the URL and doing other strict things, but would enable pre-existing MVC content to happily run within the project with its own CSS files.
I like this. At first I thought browsers would be confused by the incorrect extension, but they really shouldn’t. They should be depending on the correct content type still being returned as well as the style tags they’re being linked-from saying type=text/css.