WoT should have weather effects on different maps.
Rain, snow, fog, mist, and various cloudiness details should be implemented to give more personality to some maps. Since fighting everything at seemingly the same time gets somewhat monotonous. I realise that some people are frustrated over the limited map selection, and I will say that I don't enjoy the same dozen or so maps that I see repeatedly. And most people would believe me if I said, there's actually 40 different maps in the current game version.
However, making a fairly large, functioning, fully HD rendered map that is somewhat balanced is much more difficult than a DOOM or Happy Wheels (RIP Adobe Flash) level to build, test, and produce. It's not a process you can just open an easy editor and pump something out in an hour or two.
A drizzle of rain Himmelsdorf would look pretty neat, Mines with fog (and working lighthouse), or Cliff during a seastorm. These effects would provide a different look, but not significantly impact gameplay. The loading screen could have a faux weather forecast next to the map name i.e. Himmelsdorf: Expect severe thunderstorms.
These options would likely be limited to higher detail graphics setups, though cloudiness shouldn't impact performance and could logically be implemented to lower graphics users without issue.
If WG got crafty enough, they could implement nighttime maps with the moon providing light. And combining this with different weather could look really cool, fighting during a nighttime thunderstorm would look amazing.
TL:DR- Maps would look nicer if different weather effects were present, tank battles were not limited to just bright sunny days. Fighting during a thunderstorm or fog could look cool. While these wouldn't be separate maps, they could add some variety to what you see as the battlefield.