^^^
Unless something drastically changes by 2015, my understanding is that there are no support vehicles allowed at PBP. You could manage having a friend or relative wait for you just outside of predetermined controles ( e.g., parking lot or hotel) with whatever you need. You are right to suggest using easy to find components in case of mechanical failure (9 and 10 speed are still the most common standards.) Obviously, it is impossible to predict what could go wrong. It is sensible, however, to build an ultimate rando bike with this in mind. Having the greatest and latest technology could actually become a detriment for randonneuring.