That modern look....

Why not run 18 " front and rear. Then you can run slightly larger ratio or width rear tire and keep the typical look of bit more sidewall on rear.

Personally if I were building a car for road touring action and were purchasing new tires / new or used rims, I'd run same size front and rear so I could rotate. Then deal with offsets with spacers rather than staggered wheel stuff. Considering the cost of fancy tires, might as well rotate them... uhhh maybe.