If(when) building up a frame, I determine how i will use the bike and start with what I want for gearing to allow me to use the bike how I want.

For a road bike, that means a compact crank and relatively wide range cassette. If i dont have these things, the bike will be limited in its usability and im just not interested in limiting how i can use a bike within the segment its intended to be used.

If I want 50/34 crank with an 11/30 cassette, then I use a Sugino or Sakae crank from the 80s thats a 110/74 bcd triple without the granny ring and get the properly sized bottom bracket. Then Ill get the front and rear derailleur I want, and go from there. An older 600 tricolor short cage RD works on an 11/30 cassette so it can still look relatively 'traditional road'. From the gearing and drivetrain, i build up and figure out wheelset, brakes, shifters/brake levers, handlebars, and seatpost. I go for the stem near the end so I can have an idea of how long it needs to be to limit trial by error and reduce swapping the cockpit all out over and again to get the right fit.