I'm with those who have expressed concern over your lack of experience. I think you may have a hard time expressing what you want to a builder. It also concerns me that you are fixated on digital shifting when some additional time in the saddle will help you learn how and when to shift. It's really not a hard thing to pick up. As Tulip has suggested, get a stock bike that fits and go ride. Don't overthink it and disabuse yourself of the notion that the bike has to be the end all be all. If after riding for a few years you still feel the itch for custom, then investigate that route. By that time you'll have a better idea of how you want it to fit and handle.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher