I've converted a number of 26" wheel MTB bicycle to road touring bikes with drop bars over the last few years. One really great thing about a cbike designed for 26" x 2.0" tires is that if you put 1.5" tires on you have plenty of clearance for fenders. You also have the versatility of being able to fit pretty wide tires if you want. A 2.0" wide tires is about the same swidth as 50mm 700C tire.

Cheers