Hi Rasmus,
I wasn't aware of this functionality being added to ox-extra, thank you for pointing it out.
I've revised my patch to accommodate your suggestions and attached the new version. Now it excludes noexport tagged headlines from removal and promotes child headlines.
Using properties for this is also possible because the match string can match properties too. I just find tags simpler for this case.
I'm trying to point out that something like this is often needed and a definitive solution should be listed somewhere, preferably in the manual.
Otherwise someone looking for a solution to this common problem will end up finding only half-baked, possibly broken examples.