In PVP, if all classes are First Captain, there should be a reward.
For example, it would be nice to be rewarded with one armor or weapon skin.
Of course, PVP would also be a little more active.

If all 6 classes are First Captains, then it means that the users have put in a lot of effort.

No, unless is the same reward of PVE so you can chose the PVP or PVE route.