I write these portmortems partially for myself. It's "lessons learned" and that means that I shouldn't forget those lessons. But if you find it informative, all the better.
As for the amount of work: It was indeed a lot when I began to work this way, but after a while I got into a routine which made it all pretty smooth. But, as I said, it is somewhat error-prone, which makes testing time-intensive and leaves a nagging feeling that probably there are still situations in the game where something is displayed wrong.
Still, the main reason to bring back dolls-on-backgrounds for parts of a game is that there are situations where they simply work better.