I agree that there has to be an incentive to fly official.
The incentive has to outweigh the negative aspects of flying tagged/official, which can be HUGE.
Therefore purely cosmetic doesn't cut it, in my book.
As this is the "proper" channel, I'll repeat what I posted in the actity check channel:
Give official factions a slight bonus, like in "Select 2 that fit your faction."
> + W % hull strength
> + X % power output
> + Y % damage
> + Z % cargo hold
Some advantages that you can grasp, that really exist but are not big enough to break the system.
Let's face it, 5 % likely doesn't change anything, but it would motivate people (just watch how many players still QQ, when they "only" have a 90% core). Small changes are mainly psychologic in their effect.