So, can we have old-quantum-theory for all this (Rutherford–)Bohr(–Sommerfeld) model of an atom (and related) questions? Alternatively, we can have bohr-model for the most chemically interesting result of old quantum theory, or both since the old theory is not limited to Bohr model.
There is no reason why we should not have at least one of these tags.
Considering the comments by Wildcat, I do also agree, that bohr-model is the more reasonable choice.
I'd prefer old-quantum-chemistry because it is broader and since we will probably not deal with a whole lot of these questions in the long run we might profit from having a somewhat broader tag.
I suggest applying it to a couple (if not all) questions when there is time for it. Please consider writing a tag wiki to define the scope.