Allow the player to fight in the BR where their arsenal is most aligned. For example, if my 3 squads, tank, or plane are aligned with BR 2, and I decide to use a BR 5 weapon, I should continue fighting in the BR where the arsenal aligns up to 80%. I believe this would greatly help with balancing, especially in higher BRs, since I see many players with an entirely BR 1 or 2 arsenal who acquired one or two BR 4 or 5 rifles in some event or chest, and because of that, they are thrown into higher BRs without adequate equipment. I know someone will say “what matters is the player, not the weapon,” but this argument only holds up when you are in a BR 5 match having to face a team with machine guns and assault rifles against a team predominantly armed with five-shot bolt-action rifles (this suggestion does not include tanks and planes).
We really don’t need veterans bringing fg 42s and stingers into br 1 even in small quantities. Instead the game should show a pop up warning notification if players equipment is not good enough. You could still go to br 5 with mosins if you want to but at least you will be warned beforehand to prevent accidents.
Bringing high tier weapons into low tier matches would be not fun, If you brought br5 tanks into a BR2 match where it would be to kill it would turn people away. Instead it should warn if you are bringing low tier weapons into a high tier battle.