The default carousel ordering is:
[nation, type, tier]
This is pretty for small garages, but I find that I typically want to play a tank of a tier, especially when with a platoon.
I would therefore request the option that the order can be set to:
[tier, type, nation]
obviously, options for other orderings that would suit other people would be good too.
It's one of the changes I go and make manually every time I update.