I have not been through the free -> IAP route but each time we have to add a new permission, updates take a hit. A large part of our users never update anyway

I have not been through the free -> IAP route but each time we have to add a new permission, updates take a hit. A large part of our users never update anyway, so when in addition a manual update is necessary, it takes time. Since our app has a huge server-side part, from time to time we force users to update to mitigate this. That's not a solution for every app though.