Actually what you said was "building a dream bike with little concern for cost". Who's talking about a dream bike? (Unless your dream bike is a Veloce equipped bike with Campy compatible wheels). And why do you assume that a bike that has a drivetrain from a single manufacturer must, inevitably, break the bank?
Perhaps I was just *****ing based on how many times I had to deal with customer's bikes that had mismatched components that, in the end, were the root of the problem. (The OEs are equally to blame for this, esp when it comes to cranksets!) Perhaps a concrete example of what I am getting at is in order.
As an example: I have a 6 month old son. I can't wait to strap the little guy into a baby seat and take him for his first ride (much to my wife's shagrin, I might add). I don't think, for most people, that this will be their dream bike.
I have an old 9-spd DA group in a box, so I dragged it out, cleaned it up, and lashed it onto a frame I happen to have lying around. Small problem...no shifters. I went to my LBS and asked him to search out some shifters for me. No luck. He even contacted the distributor, who then contacted their customers (other shops nation wide) to see if they had any 9-spd DA shifters. Nada.
Now I am faced with a choice. I could snag some Veloce 9-spd shifter and order a shiftamajig and run a cable the wrong way here and tweak something else a special, secret way there and make it work "just fine", most of the time. But you know what? Inevitably, something is going to get funky with this set-up and I am going to have to spend the little time I have to ride with my son, fixing this bike - replacing something, re-tweaking something, changing a cable because my shiftamajig chews through them like candy or who knows what else.
My solution? For a bike that I'm going to use once a week, and NEVER want to have to waste my time adjusting, I am going to buy some Tiagra shifters and slap them on my bike. They will work flawlessly and for as long as I need them to until my son graduates to his own bike. I will probably never have to sacrifice a second to the shifter Gods and can enjoy the sweat sound of chain through gears punctuated by peels of my son's laughter.
My next problem is convincing our jersey maker to make one of our team jerseys small enough to fit him.
Maybe you are right. Maybe this is my dream bike.