This is an interesting approach, will try to give it a shot to the library. Thanks a lot for sharing.
In our case, for our UI Tests we are currently using DaggerMock to mock our models at the data layer level (this is, just one step further of the server response). This way we ensure our tests are not flaky (at least not because of the network…) and they run quite fast. The only drawback is that we are missing that small part that is the mapping from the response to our actual data layer objects, but we hope to cover that in our integration tests.