There were flaws with the Newk system. They didnt replicate the drop bar position. the drops were too close to the riders knees and could interfere.
Flat bar brakes and shifters dont fit onto drop bars, they are different designs. Drop bar shifters can be integrated into the brakes (Shimano STi), or fitted to the bar-ends as in the Bridgestone.
You need to take care with the cable routing. Most drop bar bikes have the gear tensioner on the downtube fitting. Most flat bar bikes have it at the brakes.
You should also note that the standard hand position on drop bars in on the brake hoods, which are 6" forward of the stem. This is your cruising position. Can you afford to move you normal riding position that far forward ? The tops of drop bars are for a more relaxed upright position, and the drops are used when cycling into the wind or going downhill.
As an alternative, you should consider butterfly style bars. These accept flat bar components but offer more hand positions. You may also be able to fit aerobars or Cinelli Spinacci bars add-ons.