No need crafting during a mission, just make sure you stock up on tonics etc before starting a mission, bit of battle prep goes a long way. Or set up your mini camp if there isn't some forced scene at beginning of mission.
Agree with you on the requirements to get gold medals though. Definately should be shown beforehand, not after. I've never been in the menus in detail during a mission though , maybe there's something in there. I'll look later.