I pretty well do exactly what you want to do. I have what is presumably a XC bike which has a front headshock (which can be turned on or off) and no rear suspension (though I installed a suspension seatpost to soften the riding a bit). I can easily switch between 1" slicks for the road, 1.5" touring tires or much wider knobby tires for trail riding. In my case, I use it mostly on-road and have installed a drop bar with bar-end levers and brake levers for an upcoming tour.

Oh, and I'm happy with the results.