Stew,
At one point you suggested midrange cassette with higher end shifters. That sounds good. The mid- and generally even lower price range cassettes are usually just made of heavier materials than the high end. They will last longer for every day riding and training. If you race, you could always keep a Record cassette on standby for those "special occasions".

Your dream bike has me drooling. Can't wait to hear how it progresses.
Regards,
Raymond