prior art

[jedwards1211]

FWIW, I implemented something similar for dealing with scalability problems in https://github.com/jcoreio/redux-utils and https://github.com/jcoreio/redux-utils-immutable.
Since often one needs to compose reducers, the compose functions in those libraries are able to look at the action type maps, and ensure that only the applicable action handlers from the input reducers are called by the resulting composed reducer.