To me it always seemed that the main problem is it takes damage from small arms while enemy light vehicles coming around the same time do not.
How about:
Scoutcar to T1, autocannon upgrade available when T2 teched
Hotchkiss at T2 as counter to allied light tanks
But as someone said, the US Lt tier would need a rework in this case or in the case of SC being buffed as per your suggestions.
That would completely remove sov T1 play, force soviets into early upgrade if T2 was to have any chance and remove brits from the game.
I love it when people make suggestions wile seeing as far as teching of their fav army goes and only that army.