Even if you think what you would say is obvious, please add. This is genuinely something I think makes sense regarding local bus routes given the longevity of light rail and how infrequently routes change, but I also suffer from confirmation bias, so I’m hoping for reasons this would be a terrible idea but obviously would prefer reasons it would be an even more amazing idea than I thought.
There are many different concepts, but generally a tram shares a space with the road traffic, hence streetcar (German: Straßenbahn). There are other terms, e.g. Stadtbahn, that are used when they are separated from other traffic.
While there are no hard rules and different approaches, I think it’s not helpful to mix up terms. A tram is not a metro. And it’s not helpful to mix modes on the same tracks, since you will run into trouble with scheduling due to vastly differing occupancy rates.