It might be cool in CON/ONS, but it'd be a pain in the arse on DM/TCM/CTF. Not sure if day/night cycling would work really, it'd be a nightmare to end up playing in darkness. There's only so far you can go with weather. It's rain/cloud/sun really. Maybe you could stick wind in their, as long as it blew trees etc around realistically and not anything that matter to gameplay (weapon projectiles, fliers). Snow would be possible, but it wouldn't settle
Having said that, I can see it working if it was backed up with a specifically made map. Imagine a cityscape map, you'd have streelights, illuminated advertising signs (which light up as it gets dark) and the like. As you'd have bright characters and gunfire etc (as well as team beacons), it wouldn't massivly hurt gameplay either. Also, if it was an "active" city, then it'd be light enough anyway
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Maybe stick a "shoulderlight" mutator for maps like that, so that you at least get an active light source of your own.