When does a component of a larger project require its own tag? Example:
So the question is, do we need/want a master
unity tag, or have all these other tags?
I would say that you can use a tag on a component from a larger project when the project it self can or not incorporate that component.
On the example given
launcher are part of Unity, they are Unity. You cannot split them from Unity.
Having a small other component that might work with Unity, even for Unity, but is really not necessary to have to make Unity work would give rights to that component to have it's own tag.
One example of that is zeitgeist. It works with Unity and even tough it is necessary to have to be able to use Unity (I think) there is a tag just for it since a lot of configuration can be done for zeitgeist that will not be directly connected to Unity.