[2020] Should there be two tier BR's instead of one?

Here the problem starts. What is "WW2"? When you want to put the line for vehicle?

Vehicle developed during WW2 but introduced month after it ends will count as WW2?

And you will be surprised what vehicles were developed before end of 1945 on Allied side. Fact, that in mass consciousness (dunno how to say it in EN) people see Nazi Germany as "high tech warfare" and allies driving Shermans and T-34 got nothing with reality of end days of WW2.