Having 3 separate queues just means there’s no reason to use BR 1, 3 and 5 equipment because it will always be the underdog counterpart.
This means that, effectively, this tiering system of 6, effectively only has 3, because the aforementioned tiers do not meet anything lower.
For example, something like a G41 will never fight bolt-action rifles. But on the other hand, it will always fight against “better” semi-auto weapons. Likewise, something as bad as ~50rpm bolt-action rifles will face 10rd ~60rpm bolt-action rifles.
How you categorized these tiers are also an issue. “High capacity SMGs” being at tiers 3 and 4 would just mean it’s nothing but drum mags dominating that BR bracket.
I’m also generally against categorizing vehicles by their relative placement to War Thunder brackets. This is an infantry game first and foremost, so not only is the ability to fight infantry a factor, it is also an integral one, and should not be dismissed in favor of a tank’s capability to fight other tanks.
This means that, with your tiering system, not only will rapid-fire HE-slinging tanks that can reload a 75mm shell every 3 seconds prominent, but the tools intended to deal with their are limited.
Notwithstanding that, among other things, you make no specific mention of where tank destroyers will be placed, and campaigns with an evidently clear gap in terms of armor role, such as the western allies, have been shoehorned into a higher tier.
For reference, a 76mm-equipped Sherman has very similar penetration and post-penetration performance as a pak/kwk40-equipped vehicle. It has no business being the “equivalent” tank to panthers and tigers before pershings are introduced.
Overall, I do not like your idea of how to fix the battle ratings. Nor are they “small”.