It should be either base building or a proper PvP mode both things the community has wanted for years.
I thought we already had player bases in ED(?) I got one that allows me to store a fleet of ships, 25K units of stuff, and other cmdrs can visit. It is persistent and it can be relocated.
Expanding the functions and activities of the existing player bases (fleet carriers) would be fantastic. More interior space, the ability to add things to it. And more customization. Am I describing base building? If so then yes... I want expanded base building.
Also, allowing a cmdr to align themselves to a specific faction & port that they could call "home", and get special privileges at that specific location would be good. Especially for new players. Maybe better prices for things, and some storage space.