Mr. Smith is missing a major conceptual issue here. The 4v4 meta (assuming roughly equal teams) boils down to Late-game Axis Heavy Tank/TD play vs. Allied Heavy Artillery/Off-map Artillery play.
Tankfest vs. Artyfest--one illustration:
https://www.youtube.com/watch?v=i4HLnIvKIBg
I actually have no major issue with this--Germans are known for their tanks, Allies are known for their arty (and, full disclosure, I am playing Allied in that above link, but I play German quite a lot and really have no preference for either side).
Actually, I think in the long run, Artyfest will win out over Tankfest more often than not. This is because Artyfest is on average better at killing infantry veterancy, and in VP matches, better infantry assets equate to more VPs held.
Nerfing Late-game Axis Heavy Tanks/TDs (either through damage or adding constraints) actually cuts AGAINST balance in my view, as a result of this--given the meta described above.
I am not opposed to "toning down" Tankfest--but only if Artyfest is toned down in turn. The proposed changes, however, tone down Tankfest far more than they tone down Artyfest. There are some changes to Calliopes and Priests, but Sextons are buffed, and all other Allied artillery--Katys, B4s, ML20s, Land Mattresses, and doctrinal call-ins--remain untouched.
Mr. Smith's stated objective is diversifying play, but this is why I think he misses the point: the changes proposed will make the Axis dominant meta less attractive (Tankfest) but it will make the Allied dominant meta MORE attractive (Artyfest) (which it does by nerfing Stuka, thus removing a risk for entrenched/indirect play). Best way to diversify play, in my opinion, is to leave TDs the way they are or perhaps make some small changes, but instead make German artillery/emplacement play more attractive, so they choose those doctrines over those that focus on TDs. Right now, it is lunacy to spend 600 MP on an LefH that can be one-shot by a comparatively cheap Allied artillery or airstrike call-in. At a minimum, LeFH needs to survive IL-2 bombing run or white phosphorus at least once, which right now it cannot reliably do. Same for Pak-43. I would even recommend making the OKW 2 cm flak emplacement not-useless to further promote the Axis artillery/emplacement doctrines.
Similarly, I think diversifying Allied away from artillery play and toward other doctrines (Mr. Smith's goal, or so he says) can be best accomplished by increasing the attractiveness/survivability of Allied tanks in the late-game RATHER than nerfing what, right now, are the biggest advantages of Axis play. The British are already fine in this regard and should be untouched (Comet). IS-2 needs to be buffed. KV-2 needs to be buffed. KV-1 needs to be buffed. Pershing needs to be buffed slightly, but is already fairly decent. So the Allies choose these doctrines instead of artillery spam.
These changes would succeed in diversifying play while maintaining balance AND maintaining an overall meta that makes sense and I think should be preserved because of the character of each faction. Right now, the changes as proposed miss the mark and actually not only will lead to greater imbalance (in favor of Allies, where Brits are already very dominant), but will also lead to even less diverse play than there is right now by entrenching Allies in an artillery/call-in focused meta.