As a very first step, offer a "must contain/exclude meat" option which would give us an average saving that trends towards 50%. Then identify the most common allergies/preferences and many people could have a typical menu trimmed down enough so that it fits one page on their mobile screen.
That's the thinking. I don't eat red meat or pork, so, for the average restaurant, my option set generally trends towards 20% to 25%. But, I generally have to browse the burger section to ensure they didn't bury a turkey burger in it.
