Is there any more or less detailed information in the Suttas or Commentaries about asaññasatta, Unconscious Devas inhabiting the 24th plane of existence corresponding to the forth jhana? They are supposed to have a body and no mind whatsoever but still are considered to be living beings. On the other hand, some of the meditation masters speak about the absence of the body in the rupa-loka. Besides, the idea of them existing sort of undermines the belief in transmigrating stream of consciousness as the connecting element of different births.
Is it really worth it, then, to develop the fourth jhana, get reborn in their world, have no idea about it because you have no conciousness and fall back to the Earth after you die there? Besides, having no consciousness they automatically skip the immaterial attainments and reach saññā-vedayita-nirodha, which is frequently considered to be the highest worldly attainment, very close to Nibbana.
Are these deities a later invention of the Indic mind who is extremely fond of creating intricate and fun cosmologies? If so, why should you come up with such an absurd idea of ‘coma gods’ that is problematic both doctrinally and emotionally? Are there any parallels to these gods in other known Indic cosmologies or are they exclusively Buddhist? Anyway, they seem to me to be the most fascinating category of deities in the traditional Buddhist cosmology.