Yea, really hard to conceptualize how it is not NPC multicrew. For example, I hire a co-pilot for my Cobra MIII (of course, FD would need to extend the existing NPC crew offering to run on any multi seat ship). But, yea I hire a relatively attractive ED copilot at some station/planet side base. Once she is onboard, I can see her when I look to the right, and she does her thing over there... perhaps some voice dialog, triggered by events in game play, or something... Perhaps no voice at all, and only text messages in the Messages panel (fits current mechanic). This would make most sense, as it would fit any play style for those lone wolfs out there along with CMDRs who want back seat live companions. Though, with live too, its a question of what you want to do? Perhaps I want to deliver Winters propaganda, or other milk runs, while my live "friend" does not. Or vis versa. Basically, there are many and likely most who do not want to be dependent upon others for their gameplay. Of course, you could opt out, but then the Commanders update has no fit for you, which does not make sense. As a generalized game play enhancement, it should benefit all.
Hopefully, hopefully.... if indeed 2.3 is "multicrew" as in seeing other avatars in the ship, perhaps in my Cobra left seat..., there should be a NPC option as frankly, I do not know who would realistically want to ride there....?!