I have modified many older steel road bike frames to be simpler, e.g single speed or IGH. My favorite is a late 70's Nishiki Professional frame fitted to a 2 speed Sturmey Archer "kick-back" hub. No cables; shifting is done by a slight back pedal. I built the hubs with 700c rims. The new Sturmey 3 speed hubs work well and they are very reliable, but you will need a shifter and cabling. A word of caution: You will need a frame with horizontal dropouts so that you can adjust chain tension. Otherwise you will have to use a chain tensioner (or elliptical bottom bracket).

Good plan - keep posting as you progress.