This is how we setup our system. We create the GUI, spawnable/changeable GameObjects, etc in a separate project. Then, asset bundle each object out for download purposes, flexibility, etc.
Would do it as just a prefab, but it is located in the GUI project and not in the login, levels, game, etc... So, asset bundle is required. I can copy and paste the object, atlas, etc in all projects anytime a change is made - but... this is not the way to go.