Right, thanks. I don't have internet out there yet but plan to. So setting up a second hub would actually be the worst-case scenario.
Many of us have found it to be the most reliable solution.
I have zero complaints about my home automation - I can't remember the last time something was slow or failed. I have 2 hubs (one z-wave, one zigbee), a Caseta Pro bridge, and a Harmony hub, all tied together by an SBC running a second zigbee network and Node-RED.
The only concern I have in placing a hub in the outbuilding is that it will be unheated. If I were to lose a switch due to the cold temperatures, that wouldn't be a huge loss. However, losing a hub during every harsh winter would be expensive.