Few points:

You can't use external auto submitters with Katz any more so even if you code your own you won't be able to use it for Katz.
Most of the main Autosubmitters have firefox plugins and support all the major DDL sites eg rardownload.net and mechosubmitter.com

If you code your own autosubmitter yes you can code your own firefox plugin for it if your able but it's a lot of work if your the only one going to be using it.