Another idea for you involves Heuristic processing. There a number of options currently but there could be a lot more added. ldolse and I spent a lot of time working with Project Gutenberg texts to make it very easy to take one and produce a nicely formatted EPUB. One quick idea is a heuristic to remove PG boiler plate text.
One other idea. A user requested to have page number in the recipe viewer. A while back I wrote a
blog post for adding line numbers to a QPlainTextEdit. This can easily be used by calibre. I haven't had the time to do anything with integrating this.
For IDEs I personally use Aptana Studio 3. It is Eclipse based and is made the the company behind PyDev. PyDev is part of Aptana. Take a look at
this thread. It includes information for setting up Apatana/Eclipse with PyDev for working with calibre.