No, Bahaullah does not claim He came from Heaven into a body. God does not move from a location to another.
He says, there is only One God. That God once manifested His attributes, Will and Words from Jesus, and now He has manifested His attribures, Words and Will from Bahaullah. Thus, just as the first Time, whoever had seen Jesus, had seen the Father, this time, also the Father has come! But this coming is not a physical moving from up to down!
I dont know where you are getting this idea that "If Baha'u'llah were to be the true Messiah he would have to have been the 'suffering servant' before being the King of kings. "
If this is what the scriptures say, please quote.
One of the reasons that I believe Baha'u'llah is a false messiah, or false prophet, is that the Messianic prophecies of the Hebrew scriptures connect 'my servant David' [the future messiah of Ezekiel] to both the role of 'suffering servant' and Judge.
The story of David gives us many clues as to the life of the future 'suffering servant' and Messiah. David was the son of Jesse, and was born in Bethlehem. At about the age of thirty, David was anointed by Samuel the prophet [1 Samuel 16:13], after which he received the Spirit [Compare Luke 3:22,23]. He was sent for by Saul and became his armour bearer [Ephesians 6:12-17] and musician [1 Samuel 16:21], shortly after which he defeats Goliath. Jonathan loves him, but Saul envies him, and tries to kill David, who is forced to flee. When Saul is killed in battle David becomes king of Judah, later to become king over all Israel. David reigns 33 years at Jerusalem, and 7 additional years in Hebron, over all Israel.
It's no surprise that Jesus uses the metaphor of a shepherd to describe himself. David was 'taken from the sheep cote'. Read John chapter 10! Then compare this with Ezekiel chapter 34. There can be no mistaking the one shepherd of the flock. The Messiah has to be of the tribe of Judah, and from the line of David.
I would now like to show you a passage from Isaiah that makes a powerful case for linking the 'suffering servant' to the Judge.
Isaiah 61:1-3.
'The Spirit of the Lord GOD is upon me; because the LORD hath anointed me to preach good tidings unto the meek; he hath sent me to bind up the brokenhearted, to proclaim liberty to the captives, and the opening of the prison to them that are bound;
To proclaim the acceptable year of the LORD, and the day of vengeance of our God; to comfort all that mourn in Zion, to give unto them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness; that they might be called trees of righteousness, the planting of the LORD, that he might be glorified.'
This passage of scripture is applied to the Messiah as the one whom 'the Spirit of the Lord GOD is upon' [as shown in Isaiah 11 and 42].
To confirm that this passage is intended for the Messiah, read Luke 4:16-22. But where does Jesus finish his reading? [verse 19]
Can you see? The one Messiah specified in Isaiah does not complete his mission in one go. The day of wrath (vengeance) is left for the future, but is to be completed by the same Messiah.