Convert Akafuku to work on 4chan?

Hello /prog/

Let me start this out by saying that I know nothing about programming.

I am a Futaba (www.2chan.net) user, and over there we have a wonderful set of Firefox extensions known as Akafuku and Aima Aima ni (http://www.unmht.org/futaba/).  These do far more than the 4chan Firefox Extension, and include such features as one-click image saving, thread archiving, pop-up windows that display the target of >>(postnumber), or even >(quote) on mouseover, extensive spam filters, etc. etc.

Having a program like this for 4chan would be fucking awesome.  I know 4chan is based off of Futaba, but how hard would it be to reverse engineer this to work with 4chan?

How can I have a Firefox ``script-let'' automatically fill out a file select element?

Doing it normally throws an exception, is there some extra code you can add to get permission from the user (I think I used something like that for XMLHttpRequest once)?

Example of what I want:
Click button -> Comment field is filled with "Japanese bird cooking spaghetti," file select field is filled with "penne rigate.jpg."