You might have better luck asking about converting it to a shed... In this area, they treat any detached structure with water or power as a possible accessory dwelling (read: living space) and make you follow the codes for living space no matter what you say. If you don't have water or power, you often can follow the much more basic rules for a shed. These rules vary wildly, if you don't want to risk being ordered to tear it down by modifying it without a permit, start first with a chat with the local zoning people about the rules. As I said, you may want to first ask if you could even turn it into an enclosed shed...

As someone else pointed out, the stud spacing appears quite far, but that can be rectified by adding extras.