Hi @sean, currently that’s not possible, unfortunately, if you are using custom builds, then you will have to manually reimage the device (and keeping the config.json to put into the updated image).
The good news is, that we have a new update mechanism that can (and will) enable your use case too! (we are already testing it for some of the pre-built images, but it’s not tied to pre-built images). The part is though, that the requirements for that are included in a newer resinOS version than 2.3.0, so if you want to be able to use it in the future, you will have to update once manually, before this new mechanism will work. More details of it are coming out soon (and we are super excited about it, some really cool use cases are enabled by it 
)