There is another site that does that already, which I found after telling everyone that I had built the the largest link list recip depository in the free world. I was wrong. But from what I'm told, their database is even more outdated than mine.
When I first built my database, many, many people suggested that I go forward and script the same project that you are proposing to do now. But I didn't, and it was due to pretty much the same reasons that have been mentioned here already. It looked like more hassle than what it would be worth.
One of the bigger hurdles is the fact that not all link lists have the same categories or even define like-named categories in the same way. Plus, many have split major categories into soft and hard, ie - Ebony and Ebony Hardcore. It becomes a situation where there are so many options that need to be scripted to ensure the correct recip table is built, that it becomes a somewhat user-unfriendly script.