First, markers are meant to be retrieved in static-content. I cannot grasp why this hinders us.
Markers are pieces of contents associated with areas in the area tree.
That's how they are going to be used in my proposal, the semantics didn't change. To retrieve or not to retrieve is at your option. The same is true for any extension. In my proposal, I use this property to instruct the renderer to pick up a piece of contents that would otherwise be dropped, and use it for purposes that don't interfere with the formatting. I don't feel I am abusing it.