Of the above analysis , which one is correct?

Dear sir,
The following sentence is selected from Economist.
What some scientists hoped would be a
blitzkrieg has turned out to be a steady but
successful war of attrition.

The meaning is not difficult to understand. However, I was puzzled at its grammar structure.What part of speech each part is?

The following is my analysis and wonders.

What some scientists hoped would be a
blitzkrieg /(subject) has turned out to be a steady but
successful war of attrition.(predicative)

But the subject What some scientists hoped would be a
blitzkrieg has already been a complete sentence. The what-clause What some scientists hoped can be the subject of would be a blitzkrieg .

My wonders are as follows.
1. Whether the part some scientists hoped can be reguarded as inserted part of the whole what-clause (What some scientists hoped would be a blitzkrieg)?
2. Others argue that the part would be a blitzkrieg is an objective clause, serving the object of the verb hoped.
If this is possible or correct, the subject of the objective clause can be omitted? Or which part serves the subject of the objective clause?

3. Personaly, one of my grammar explanation for the original sentence is the ommit of "but it ".That is:
What some scientists hoped would be a
blitzkrieg,(but it )has turned out to be a steady but
successful war of attrition.
Of the above analysis , which one is correct?
I'm looking forward to your authentic reply.