The question, of course, is whether it will scale to more complex cases with more elaborate option documentation (i.e., multiple paragraphs, formatting, short version for usage, extended version for man/html, etc).

For C++ there is the CLI compiler that implements a similar idea (i.e., uses a DSL) but instead of using the usage itself as a specification, it is based on the class-with-members abstraction. While the result is not as terse, it is quite a bit more flexible. Plus it allows you to specify option type (i.e., int, double, string, etc).

From a single interface specification CLI will generate C++ parsers, usage printing code, man pages, and html pages. Here is an example of a real-world interface that is handled with CLI:

http://codesynthesis.com/products/odb/doc/odb.xhtml

The project page is here:

http://codesynthesis.com/projects/cli/