In between you doing that and me thinking on it overnight, I ended up writing up my thoughts as a blog post [0], which I have submitted here to HN as well [1].
[0]: https://matthewsinclair.com/blog/0177-what-if-we-taxed-adver...
[1]: >>43620407
[0] Slightly tangentially, to be ignored, until later (after careful reconsideration of doubts raised in your [1]: https://economics.stackexchange.com/a/29610[2])
In particular, to consider how unification of the 2 notions of excludability/rivalry can lead to the 2 actions of subsidies/taxation coalescing (thus going "beyond good & evil")
[2] >>43621295
[4] https://www.econlib.org/the-correlation-between-excludabilit...
>Yet in the real world, both excludability and rivalry lie on a continuum.