Yes, but not without modifying one of our shipped .e files, which usually isn't recommended. (mainly because applying a hotfix that updates the file you changed will revert your changes).
Two things. In cformat.e, look for DEFAULT_BEAUTIFIER_EXT, and add " ruby=ruby" to the end of that string. Save it and run "load" at the command line to load your changes. And, then rename your command to ruby_beautify(), and then reload it as well.
Once that's done the 'beautify' command will delegate to your ruby_beautify() command, and the option will be enabled in the Tools -> Beautify menu.