This is what you have to do to define a projectdoc document:

1. Add the Document Properties Marker Macro to define document properties
2. For each section of your document use the Section Macro

The page author usually selects a page template with a blueprint wizard. So there is no need to add the properties or section macros manually.

The template author adds the properties and sections at the time she defines template. This is a one time effort and employing macros instead of simple text makes not much difference.

If the page author adds a property, this is a new line in an existing table. Nothing to worry about. If the page author wants to add a new section, she may choose to not use the Section Macro. In this case the content cannot be transcluded. That's all. If the author wants to support transclusion, she has to select some macro anyway. So there is no difference in using projectdoc macros or macros provided by other vendors.

So we think the effort on using macros is quite low.

You have to invest into learning projectdoc.

If your authors like to invent a new document structure for each document they write and feel limited by the use of templates, then projectdoc might not make them very happy.

projectdoc leaves room to adjust documents to present the information. It does not demand to follow a defined template. To the contrary, the template is a best practice to write documents of a given kind. So adding new properties and sections and not adding specifying ever property and filling out every section is fine. Actually it is the responsibility of the author to decide which information makes sense. But if an information is required to meet the reader's expectation, the template defines where she expects it to be found.