Oh I think a proper weather system and day/night system IS complex. And I mean a proper system, where people actually realistically reacts to the environment condition. You can't expect a painter to hang around under the rain at night, on the town's central plazza, to sell his paintings. Not only would the guy be nuts not to run to cover and/or near a fire, but he wouldn't let his paintings risk being damaged
And that's just one obvious example. In the end, Larian isn't willing to have a purely cosmetic system of night and day, neither are they really interested in dedicating ressources to NPC behaviours...
On the other hand, sure, weather may be a tad easier to implement, especially since they already have static weather conditions in DOS1. Just make them dynamic, maybe force a specific weather upon towns or quest hubs in general. Either way, with or without, I'm okay with what I'll get.
