All of those reduce the effectiveness of indirect fire at clearing out anti-tank positions.
Those changes could well be improvements to teamgames, but they won't make medium tanks more effective in them.
That's why I didn't say nerfing only Arty would solve the problem.
The dozer is "upgrade" is not interesting and after the patch it will cost fuel and manpower not MU.
The majority of Allie medium do not need buff or upgrades, they are cost efficient. The main reason that they do not see action is that Td/infatry spam is better/safer choice.
The dozer upgrade on itself is an interesting change, I didn't say anything about its actual cost or efficiency. I just pointed that such upgrades are the way to go to make medium relevant on the late game.
On the other hand, TDs aren't the main reason why you stop building mediums, TDs are a part of the reason but, and this is my opinion, not the main factor.
From my game experience and cast I've been watching, TDs alone can't kill medium (unless bad play such over-extension), there is always a combination of various factors and the most critical one being the engine damage dealt by an infantry squad around the corner.
My opinion is that medium tanks suffer much more from damage engine than any other tanks which is exactly what make them so unreliable late game since they need to close the distance and take risks to achieve their goals in case of offensive.
Now imagine such individual upgrade only available for medium tanks that would change the damage engine trigger to 50% from 70% (example), that would give an interesting opening for mediums to fight TDs and infantry since they're less likely going to be rooted by the 2nd and finished off by the 1st.