No need to even use focaccia - many restaurants will serve cheeseless pizza, or you can make it at home. No need to use cheese substitutes either, Just get a nice crust, brush with olive oil, add sliced or diced veggies, maybe tomato sause, and bada-bing.
Olive oil instead of buttter - getbseveral brands and styles of oil. Look for the Low Hholesterol Olive Oil Cookbook -
Amazon.com: The Low-Cholesterol Olive Oil Cookbook: More Than 200 Recipes - nice recipes for many dishes using OO instead of butter.
Shel