Originally Posted by
ljsense
If you take brake/shift levers out of the equation, which are an obvious step forward, I think downtube shifters are as good as anything.
First, the front derailleur cable has no housing, just a bend at the bottom bracket. The rear derailleur has one section of housing from the chainstay to the derailleur. The reach to the levers is less than the reach to a water bottle. So if you're able to access your water bottle, you can easily reach your shifter.
If taking one hand off the bars is a deal braker, explain a shifting system of that era that didn't at least occasionally require this? Bar end shifters are often ridden by riders who don't spend all their time in the drops. Stem mounted shifters will always require lifting a hand. What other options did you have in mind?
All of the above + this: I used to adjust both derailleurs with my right hand. I could trim my front derailleur while shifting the rear derailleur.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.