I really appreciate an Italian who isn't prescious over pizza! Of course, traditional Italian pizzas are great, but that doesn't mean alternatives can't be awesome too!
IMO, so long as the toppings go well with the sauce (eg a fajita pizza should have a spicier sauce) then you can make something great.
I've had (sweet) potato work on a pizza before, the pieces need to be pretty thin to cook properly. The octopus was overcooked on that one and the potato were large chunks and undercooked.