Shipsets, Empires, and dead AIs

Is there any way to add a shipset that can be used by human players but that won't get picked for an AI, which then sits and does nothing until you conquer it?

I think I saw this even in stock, but it's a big problem using the BM because there's no chance at all that the AI scripts would be right.

The first time this happened, I figured it was a bad AI script so I deleted all the compiled scripts from the offending "Empires" subdirectories. I expected that the generic neutral race AI would be used. But it still happened. Am I on the right track, and I just have to delete some of the .txt files (racial settings, etc.) too?