Hmm, I think it could prove a problem for the part of your theory which claims that the Listeners have no obvious connection to humanity; the Listeners' ability to interbreed with them is definitely a connection! If we accept your main point that the Listeners predated humans on Roshar, then it seems more likely that they were a creation of Adonalsium than naturally evolved lifeforms, as Adonalsium would have been able to create Listeners that are genetically similar enough to humans for the two species to be able to interbreed.
On a slightly related point: do we know that Honor created all the human societies on Roshar? I seem to remember reading theories that different cultures (specifically the Shin) came from other planets...