I regard kaeshiwaza as a way to refine the aikido techniques, so that they become less and less possible to counter. That means kaeshiwaza should by time be impossible to do - but that takes a lot of time.
You see your two hands holding my wrist mid-shihonage; I see you attacking me with morotedori. If your shihonage is impossible to counter, then there is a morotedori attack for which Aikido does not work.
That would be unfortunate for Aikido, no?