Very many good observations here!
If I may add a little wood to the fire :
The "sense" of the final yeov in John 1:1 is without question qualitative. Insofar as the predicate anarthrous kai yeov hn o logov is concerned, Dana and Mantey point out (A Manual Grammar of the Greek New Testament, p. 140):
Surely when Robertson says that yeov, as to the article, "is treated like a proper name and may have it or not have it" (R. 761), he does not mean to intimate that the presence or absence of the article with yeov has no special significance. We construe him to mean that there is no definite rule governing the use of the article with yeov , so that sometimes the writer's viewpoint is difficult to detect, which is entirely true. But in the great majority of instances the reason for the distinction is clear. The use of in Jn. 1:1 is a good example. prov ton yeon points to Christ's fellowship with the person of the Father; yeov hn o logov emphasizes Christ's participation in the essence of the divine nature. The former clearly applies to personality, while the latter applies to character. This distinction is in line with the general force of the article...The articular construction emphasizes identity; the anarthrous construction emphasizes character.
Archibald Robertson says (Word Pictures in the New Testament):
And the Word was God ( kai yeov hn o logov ). By exact and careful language John denied Sabellianism by not saying o yeov hn o logov . That would mean that all of God was expressed in o logov and the terms would be interchangeable, each having the article. The subject is made plain by the article ( o logov ) and the predicate without it ( yeov ) just as in Joh 4:24 pneuma o yeov can only mean "God is spirit," not "spirit is God." So in 1Jo 4:16 o yeov agaph estin can only mean "God is love," not "love is God" as a so-called Christian scientist would confusedly say.
Oscar Cullman (University of Edinburgh) says (The Christology of the New Testament, p. 265-6):
Thus the third phrase of the prologue can actually proclaim kai yeov hn o logov ( and the Word was God ). We ought not to reinterpret this sentence in order to weaken its absoluteness and sharpness. There have been and still are many attempts to do this . yeov has been interpreted as if it were yeiov : 'The Logos was like God.' This interpretation is hardly possible, and R. Bultmann too has rejected it in his commentary on John (p. 17). If the author had intended to say this, the adjective yeiov was at his disposal; it occurs elsewhere in the New Testament (Acts 17.29; II Peter 1.3).--It is also not feasible to weaken the statement as Origen attempted to do by arguing that in omitting the article before yeov , the author intends to say that the Logos is not actually God but only of divine nature, a divine emanation.
In this last comment Cullman refers to yeiov (root form yeiothv)( only in NT at Romans 1:20), an adjective that, similiar to but much less forceful than the related adjective yeothv (only in NT at Colossians 2:9), explains much more about the Biblical concept of the deity of Christ (See Trench, pp. 7-10). If the commonly accepted chronology of NT epistles and gospels is correct, then John was well aware (at least via Paul's writings) of these other 2 words, and could very easily have used either one of them in John 1:1c instead of the much more direct (though anarthous) yeov. This in itself is very suggestive that John 'intended' to be much more direct in asserting the Divinity of Christ.
Insofar as the 1st-century development of this doctrine is concerned, Moule (Cambridge) makes the following comment (The Origin of Christology,pp. 136-7):
For my part, I hold no doctrine of the inerrancy of the New Testament, no brief for the view that every estimate of Christ within it is to be accepted uncritically, simply because it is within the canon. But my belief is that it is the more individualistic Christologies, such as that of Luke-Acts, that are less adequate and less close to the original than the more inclusive Christology of Paul; and it seems to me that, with the latter (and with many of the implications even of those more individualistic Christologies), go the very highest Christologies that are to be found in the New Testament.
Myxo, your quotes of Irenaeus are right on the mark in this respect. One of the eye-openers for me was when I went back and actually read what the early 'church fathers' wrote, instead of lamely accepting what the Trinity brochure selectively quoted out-of-context. And, lo and behold! there is a much stronger vein of 'Deity of Christ' in those 1st- and 2nd century works than the WTS ever admits (what a surprise ). There was definitely a 'development' of this doctrine over the course of many decades, but by John's time it had reached a fairly finalized form (though the issue of homo[i]ousianism still remained ).
Loris and herk, along the lines of what you say, it's interesting that Phillips renders John 1:1 as
AT the beginning God expressed himself. That personal expression, that word, was with God, and was God.
Also, there is a privately published Concordant Literal New Testament (1983) that reads:
In the beginning was the word, and the word was toward God, and God was the word.
These 'impersonal' renderings are totally allowable, insofar as grammatical rules and otherwise typical usage are concerned.
It's also interesting to note that, in the opinion of some, the first 18 verses of John were not actually written by John, per se, but were included by him (or, perhaps added later) as a hymn that was sung in the early Christian church; note for example how The New Jerusalem Bible presents this passage.
Insofar as Hellenistic influence on Christian doctrine is concerned, well...that's more than I can get into right now.
Again, interesting posts by all!