I'm all for weather effecting the monsters that show up in the world as well as elemental damage bonuses/negatives from weather effects.

Not so much on the gear though, as hot-swapping gear isn't really a thing for the game it would be pretty situational. I think SE wants to avoid people building specific "Sets" of gear. But what do I know could be a usefull materia stat at least to give people a choice over functional (HP whatnot) over situational.