Hi Ryan,
There is not currently an option to sign the artifacts created by the server and in fact to do so would be a security issue since you would have to upload your private key to do to. Other than that it is identical to running mender-artifact locally. Even when using the UI to create the artifact, the Single File update module must already be installed on the client. If that is not an option then the best choice would be to deploy a full image update where the only difference is the addition of the new module.
Drew