Interesting. This will be helpful if I wanted to use a scheme macro (are there any?), but otherwise I would probably just use the mz patch, using the pattern that showed up for the $ macro:
It almost looks like a package reference, and it gets all of its arguments directly from arc, because it's just returning the procedure and calling it on the arc arguments. It won't work for macros, because those transform code, but it works pretty well for everything else.