It looks like there's makepkginfo support for this, making it seem such that makepkginfo could be executed against a .mobileconfig file, then the resulting plist could be uploaded to Simian.
In a quick search through the Simian codebase, I can't find any requirement that package uploads are of type "dmg" or "pkg", so uploading a mobileconfig should be possible.
Can you remove """ accept="application/x-apple-diskimage" """ there, make_release to upload a new server, try uploading a plist resulting from makepkginfo against a mobileconfig, then try uploading the mobileconfig as you would a dmg?