The middle component is ambiguous, and there is no reading or meaning provided.

Looks to me like the Buddhist term 三昧 with mouth radicals added. The middle component is clearly 日 and could not be anything else. Of course, it is desirable to know the reading and meaning of every proposed character, but that is not always possible, and in the case of mystical syllables used in Buddhist and Daoist texts there may be no specific meaning. The primary purpose of encoding the Daoist-usage characters proposed by the UK is to enable the representation of these particular texts in electronic format, and it is not necessary to know the meaning or reading of these characters to do this. It should be noted that many already-encoded CJK unified ideographs characters, as well as some characters in other extinct scripts such as Egyptian Hieroglyphs, Tangut, and Khitan Small Script, have unknown meaning and pronunciation. The primary criterion for encoding characters is evidence of usage, and we believe that the evidence we have supplied for the Daoist-usage characters is very solid.