In an open PvP world I'd be against letting gatherers/crafters be removed from pvp or given a strong stealth. This would lead to people using them to scout for targets of opportunity, or to escape from a fight.
Imagine being out in the world, nobody in sight, so you start fighting a fate or hunting target. And then someone unstealths, switches classes and one-shots you. They then immediately switch back and vanish or become immune to retaliation. This is not fun; you need to have some reasonable way to avoid them or fight back.

At the very least, switching classes would have to be restricted in some way outside of personal innrooms.