Very interesting topic actually.
One important and fascinating aspect of the Revelation "of John" is its complex relationship with the religious and literary movement we call "Johannism" (reflected the Gospel and epistles "of John"); in a major sense it is diametrically opposite at least to the Fourth Gospel inasmuch as it promotes a futuristic eschatology, whereas the thrust of the latter is realised eschatology. But this should not conceal the many verbal and conceptual features they have in common -- they may have developed in the same region (Asia Minor) after all. There are indeed a number of similitudes in the allusions to (and re-interpretations of) the divine name among other things. And the extension of the Deity (which the name stands for) through Christ to the elect, which is an essential feature of Johannism, is indeed perceptible in many images of Revelation.
That is interesting about the number of the adjective(?) conceptually allowing for name or names in 14:1.
Actually a verb, passive participle perfect of graphô.
Are there any good reasons for deciding between seeing that as deliberate or unintended ambiguity on the part of the author?
I don't know, but I'm not sure it really matters.
The phrase “The One who is and who was and who is coming” (literally, "the being and the was [sic] and the coming," a school case of solecism) is widely understood as a development of the interpretation of Yhwh in Exodus 3 (LXX, ho ôn, "the being"), which distinguishes itself from similar Jewish formulae by the substitution of "coming" to "will be" in the last term -- the "coming one" being precisely a Messianic title, think for instance of John the Baptist's question to Jesus, are you 'the coming one'?
The main thing JWs (and perhaps you) do not understand about this topic is, imo: it is precisely when the name Yhwh gradually vanishes from current usage (starting with the shift to monotheism, when it loses its normal polytheistic function, i.e. distinguishing a god from other gods) that it becomes available for interpretation (starting from Exodus 3). The less it is literally used the more it can mean; "the name of God" becomes an empty placeholder, a signifier without a concrete signifié in everyday usage, which all sort of theology and mysticism (and also, sometimes, esoterism and magic) rushes in to occupy.