I would have to say it is about choice affecting actions. It is evident that the previous Neo's chose different paths and their actions were affected by it. This Neo, through his love for Trinity, chose a different path and the end result was just that; a result of choice. Was it his destiny? I believe it was the predetermined destiny of all the other Neo's, but the choice had to be made for it to become a reality.
The Architect had to let Neo choose, so that his actions would allow the rest of the humans to now make the choice of living in the matrix or not. If the Architect simply made it that way, humans would not be human, because to choose is inherently human. The Architect had to let the humans hero (Neo) get the oppotunity to liberate them, and then and only then would they believe that now through Neo's conquest that they had a choice, not because of the whim of the Architect himself. Of course he wanted no part of it because more humans than before would choose Zion over the Matrix, even though my inner belief is that Zion is just another form of the Matrix.
Good point again, but that leads the further question... where is Smith in this? Is it that the Architect saw that Smith was overriding the system and so the only way he could stop it was the human element? It is obvious that Neo has built in powers given to him by the Architect - was one of those powers to lead him towards Smith? Was Morephus also another form of Neo - a person bred to believe and get others to believe?
Yes, the Architect knew that Neo would be able to defeat Smith, which is why he wasnt jumping up and down about it. Smith's role was to convince and inevitably show Neo how to liberate the humans. Morpheus, even though he was a great leader, was a pawn in the entire equation. His role was to find Neo and liberate him from the Matrix, and that was it. In Revolutions, Smith was not even an agent anymore, because the Matrix agents saw him as an enemy, not an associate. He was now on neither side, he was a one man wrecking crew bent on total rule over the entire Matrix. However, he was still a program, a very powerful program, but still a program, and the Architect knew fully well he could be and would be destroyed by the most powerful program of them all, Neo.
Sure but then the question still remains... why does Neo even have to do anything with the Humans? Surely if the real intention is to get rid of Smith then the Machine (Architect) simply has to say to Neo without making it so difficult or in other words assist Neo in the Matrix as well not only during back door sessions. Or probably the Architect walks a rule of law that does not allow him to 'fraternize' with humans in this way?
He really didnt have to do anything with or for the humans. However, he realizes how much faith the humans have put into him, and uses this, and his love for Trinity, to defeat Mr. Smith and make the alliance with the machines. The Architect realized a long time ago that his direct influence on the humans would not bode well, so he left it up to the humans to resolve their own issues, and he is just the overseer. He gives direction and a Choice to Neo, but that is his extent of interference.