I've wanted some kind of weapon switch talent or ability or weapon mod (or all three) since the original. Not sure if a default free weapon switch on cooldown (3-5 turns) would be too big of a deal either.
Armor switching a whole set in combat might be a bit much. Like, does switching to a cripple immunity chestpiece cure cripple?
As far as out of combat gear switching goes, that would be convenient, but I've said it before, and I'll say it again, I really don't think equipping a bunch of lucky charm gear to loot some boxes or charisma gear for talking, or pickpocket gear for stealing really makes for good game design. I just feel like they should make individual points in civil abilities slightly better, or just give you civil points more often, and remove civil abilities from gear, so stuff is balanced around base points instead of presuming you're equipping +charisma gear or what have you.
I hate to reduce the variety of gear even further, but interesting loot can be solved in other ways than a constant feeling like I need to play dress up to get the most out of the game.