I'm not a fan of butter on most sandwiches, and certainly not crisp ones, which during one exchange a few years ago led to somebody call me 'Anti-British' :)
Believe me there are fair more important ways I might be considered anti-British without bring butter on sandwiches.
Nacho sandwich sounds good to me. A plain cornchip with a drizzle of a tomato based dip on warm thick white bread sounds less like a sandwich and more like a religious experience to me.