I was quoting the other guy earlier on how he said having dynamic weather in low level areas might make it too difficult to do anything, in which I replied the content at lower levels is laughably easy and if it did become a bit more difficult (which I doubt, it doesn’t add combat advantage to mobs and at most, it just limits visibility), it still wouldn’t be enough to make it impossible.
As for implementation of this system, Guild Wars 2 has high hopes of having such a system. If you notice when you enter a cave or something, their lighting system is client based. That means it depends where you are standing, changes the light source around your character, etc. You can test this when you enter the cave in Dry Top: as soon as it goes dark, turn around. The outside will be dark as well, indicating its client based. It wouldn’t be difficult to do that based on a timer for an entire map. It would be difficult and time consuming if it were based on where you were standing, but we are talking about whole zones here: the only places they would have to disable a feature within a zone are places where you have to go inside something. And there’s not too much of that is there.
And lastly, concerning the champion train: it is not a supported feature or anything, true. That doesn’t change the fact hundreds of people do it every day in the same maps. What ANet could do here is, even without the weather system, turn that champion train into a better feature. It’s already part of a daily, how about a reward for making one full round? The catch is that the champion mobs only spawn in maybe 1-2 maps only for the day, or maybe even for only 3-4 hours at most, or maybe even just a few rounds only. The idea behind this is to turn something we already have, make it a little better, and make people go around all over Tyria, including the least favorite and least populated maps, a lot more often.
Having weather change would further make it feel different every time, despite them being on the same map.