A123 : by Tony Garland 
Although God most certainly is not a man (Ex. 20:4-5), or a mere figment of Israelite imagination as you suggest, it is a valid question to wonder why God, in certain circumstances, chose to manifest Himself in human form?
I think the answer has to do with relationship. Genesis tells us that man was formed in God’s image (Gen. 1:26). Although this undoubtedly refers primarily to non-physical attributes (love, creativity, imagination, altruism, justice, conscience, etc.), it does seem evident that man was created for fellowship with God (Gen. 3:8).
When trying to answer this question we should bear in mind that one of God’s primary purposes throughout Scripture is to reveal Himself to His creatures. Therefore, at times He appears in visions as a man (e.g., Eze. 1:26; Dan. 7:9 cf. Rev. 4:2-3) in order that men can more readily grasp aspects of His character as reflected in various anthropomorphic descriptions (e.g., “the hair of His head was like pure wool”). Thus, I believe that the man-like appearance of the Father in many visions is primarily a method of communicating truths which our limited experience can take in.
There is also the problem of sin. Initially, man had full fellowship with God. But, at The Fall into sin, man became tainted with sin and unable to be in the presence of God’s unveiled, holy glory (Ex. 33:20). From that point forward, God’s localized presence (Ex. 33:14-15) was manifested in various forms—often referred to as theophanies, sometimes referred to as “the Shekinah” " (from the Hebrew root שׁכן [šḵn] — to dwell).
These theophanies—appearances of God in alternate physical manifestations—account for the physical limitations of man, yet allow God and man limited interaction: always separated in measure by the reality of sin.
The “Angel of the Lord” is one such manifestation of the Deity, in the form of a man, which is found in many places in the Old Testament (Gen. 16:7; 22:11; 32:24; Ex. 3:2; 23:21; Num. 22:22; Jdg. 2:1-4; 6:11; 13:3; 2S. 24:16; 1K. 19:7; 2K. 1:3,15; 1Chr. 21:18 and probably Jos. 5:15).
These man-like appearances of God find their ultimate manifestation in the incarnation of Jesus Christ — God in the flesh (John 1:1-14). In fact, Jesus, in the incarnation is the revelation of God in a way which man could interact with—handle and touch:
And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth. (John 1:14)
The word for “dwelt” in the above verse is εσκηνωσεν [eskēnōsen] which is similar to the Hebrew root שׁכן [šḵn] used of the Shekinah. This seems to be what John has in mind as he indicates that in the incarnation, the very glory of God was able to be beheld—and even handled—in a way which was never possible before!
John goes on to imply that God has never been revealed in Human form except that Jesus was that manifestation:
No one has seen God at any time. The only begotten Son, who is in the bosom of the Father, He has declared Him. (John 1:18)
So, the idea of God taking on the form of a man has to do with His preparing to reveal Himself to us in a way which we could relate to and which avoids consuming us because of our sin.
If the Creator chose to stoop down, out of love, to interact with His limited creature, what better way than as one of those creatures—all the while retaining His divine nature (Php. 2:6)?
This intimacy of God with man found its ultimate expression in history when the Son stepped down into His own Creation within the confines of creaturely existence via the virgin birth. This is an immense mystery and illustrates the degree God was willing to go in order to reveal Himself to His lost creatures!
This truth will never bow down before the puny rational intellect of men. But those “who have ears to hear” revel in the immensity and mystery of it!
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