I'm not necessarily surprised that multi-crew is combat only. The mechanics for the rest of the game, exploration most notably, are way to underdeveloped to utilize multi-crew.
What I was hoping, and I am sorely disappointed didn't happen, was that Frontier would improve on the other mechanics in preparation for multi-crew.
We haven't been given the full list of features for 2.3 yet, so there is still a chance that maybe exploration mechanics have been improved.
But let's take a look at the feature itself, how will combat benefit? I don't do PvP, so I can't be sure, but from what I have read about it. PvPers have very specific builds and tactics. Multi-crew would require changing those builds and tactics, too which, I might add, would(most likely) not be as effective as the original(non multi-crew) pvp builds.
As for PvE... well... it could work, BUT there is a problem. The majority of PvE is farming in resource extraction sites or combat zones. I don't see that as fun for multi-crew. I also see numerous problems arising with Turret or Fighter Con aggro-ing every npc in the area and getting the Pilots ship destroyed either accidentally or intentionally.
If Frontier could make PvE more scenario or objective based(protect convoy, assault base), I could see multi-crew being fun and an asset.
Right now, I see it as being incredibly underused and niche. Which, in turn, makes it a waste of Development time and resources.