Imagine this you have a great mg amazing stability, the problem is that you will get blown off as soon as you leave the battle.
What could fix this -
Armour not enough to make you a full blown tank but just enough to keep you from experiencing the pain of 7.65 ripping through your head.
Germany and italy can get the L33 and the Panzer 1
Japan gets TE-KE tankette
the Soviets get the T-27
and the allies can finally get the long awaited Bob Semple World Destroyer
or the T16/T14 if you wanna lame gaijen
its a perfect fix and gives more reasons to bring AT rifles at high tiers
depends on what weapon they carry
for example L3 had in addition to the classic 20mm
versions with Breda SAFAT 12.7 and Breda Mod.31 13mm machine guns
against vehicles BR1 is more than sufficient (especially thanks to the limitation of BR1 it would not encounter other BRs) and also what ammunition they put on it can also make a difference
There could be like a tier system like the tanker classes where you start off with the simple machine gun tanks, before moving on to the more powerful tankettes armed with auto cannons and finally the flamethrower variants making them ever more terrifying on high tiers