I agree with this idea.
War Thunder would be the best example, due to its plenty free customization choices.
They should bring in how if you ever buy a decal, you own it permanently, and can use it in more than one slot, than having to buy it all separately:
And of course, the roundels and insignias which are missing, and crucial for specific factions. It can also add variety for tanks that are donated in instance.
They should make some decals free and unlockable by completing certain amounts of
kills or winning a certain amount of matches in a certain nation to unlock them.