Right, these laws absolutely should change. I would hope that any municipality facing a problem like this, with lots of empty office space, would also recognize the fact that their zoning rules are a bad idea.
Sometimes offices are empty because banks that own them dictate the lease rates and building managers can't adjust price to fit the market rate. I sometimes think city councils and codes get too much heat on this issue and the 800lb finance gorilla in the room is politely ignored.