Thanks for the response Danny.
I have a bit of experience with MySQL/PHP, and have a suggestion for you: you could rebuild MySQL to accept 2/3 letter searches, and then programmatically check the search input using PHP. That way, if it is not in the list of exceptions, and is less than four characters, it would not get submitted to the MySQL database search function.
Hope that makes sense. PM me if you need clarification.
Si