You might get better answers if you contact the Jython developers themselves and look at their wiki - http://www.jython.org/cgi-bin/wiki/FrontPage. Even though you found the posting on a Python wiki, you really want to consult the Jython community, and I'm not sure to what extent they participate in this newsgroup.
Just by reading the description of the task and your post I'd say the project is certainly doable, but not trivial. Since IDLE is a Python application the path of least resistance would be to port it to Jython. The majority of work would probably be in replacing the Tk GUI with a Java-based GUI. You say that your people have experience with Swing so you have a leg up on that part. Since Jython currently does not support all of the latest Python, you likely will have to work around some features incorporated in the latest IDLE. As you say that your team has limited experience with Python, this might be the most challenging part. I'd ask here just how much experience your team has had with maintenance programming. Modifying someone elses code is a different task than writing new code from specifications, and some programmers dislike this kind of work. I mention this because I think that designing and building an IDE from scratch IS more than you want to tackle. You might want to look at some of the other IDEs that support Python. One of the things you'll want to do is reverse engineer IDLE. If you are currently using Eclipse for Java development, there are a couple of plugins for Python which should support Jython to some extent. Bill -- http://mail.python.org/mailman/listinfo/python-list