Honestly they could fix A LOT of problems players are having by letting players to be able to start a faction ...
Seriously.. Imagine two giant factions of PLAYERS fighting for territory like NPC factions do. It would be glorious to see what people come up with as far as Giant battles while trying to fortify or prepare or attack.
If they allowed players to create there own corporations and slowly turn them into super powers.. Could you imagine the amount of content that could be had with an update like that?
Well, we do have 400 billion star systems so a few of those could be dedicated to player ownership. A persistent territorial struggle would be interesting. I don't know how 'massive' battles could be with the peer-to-peer structure of Elite but I'm sure some fun could be had.
But seeing how we still have threads pining over the abandoned off-line mode, expect heavy resistance to guilds/corporations and other multiplayer aspects of the game.
- - - Updated - - -
Finally, of course: how are player groups supposed to "protect their territory" when you can just duck into Solo and avoid any pesky player-created blockades or checkpoints?
Designate (and re-code the game appropriately) some systems as 'Open mode only'. The only way to get there is by going to Open. Kinda like how you can only get to some systems now if you have a permit.