So, since I'm in a clan, I get Tours of Duty with all the free cosmetics that implies. And I've also collected some elements from events and anniversary shops, also. Kind of sad I missed the Highway Rock event last summer now that I'm looking back on the news, but my motivation to play this game was kind of low at the time.
First off, customization elements (other than all-season styles, obviously) should come in threes. Emblems for summer, winter, and desert, camos for hull, turret, and gun. Especially the nation-specific ToD camos. I can just see myself waiting forever to finally be able to do up an entire tank-season with one pattern, especially given that they seem to come with a "one tank only" stipulation (does that still apply once you've got more than three of the same kind for the same nation?)
Second, once you've earned or purchased a limited-time customization element, you should have the option to purchase more of it later, even once the event has ended. I don't even care if this means spending gold. I don't even care if this means spending a lot of gold. It's incredibly annoying when you go to apply some event customization element, and realize that you forgot to buy it in multiples of three – or, on the other hand, were only ever given 1-2 by the event. And now the event is over forever, and the Black Market never sells 2D customization elements as far as we know. So then you have to find something else (or nothing) to occupy that slot for the last season, and the dream of having your tank be the same except for the camo pattern in every season is forever smashed. Having to buy duplicate progressive elements for gold is annoying, but it's better than being permanently forbidden from ever having them on more than one season – this system should be adapted to other customization elements.
Also, ToDs not assigning new tasks. I have 1400 points left to get the last camo from the current one, and "New Tasks will be assigned once the next Tour of Duty starts." ARGH.