I personally like the suggestion made somewhere on the old forum of players with a badge can't hit the fortress or get a new code. They could still control the world and their, sometimes many, alt accounts could still get through to the centre.
The main issues are, as I see it:
1) multi-accounts used in various ways as a way to help the main account and not played for their own sake and benefit
2) No 'endgame' option after the fortress is available.
The game is basically still a 'king of the hill' game and as such the biggest 'kings' control a world.
We've all seen many suggestions and some of them have been implemented, but none so far that address the problem that to become 'king of the hill' (controlling the centre) you need to spend a large amount of time and effort and as a result banishing members to the edge of the world or suggestions punish those that spent the most money. Which company in the world would alienate it's customers in that way - "the more you spend the more we punish you!"
The veteran servers were an attempt at providing alternatives for old world players to move over. In my view they were implemented poorly in terms of gameplay to do that. Everyone starts with one level 45 base (or enough resources to get to that level) and from then on it becomes a similar game. The VP scoring helps and was intended, so I believe, to attract players from other worlds.
I would prefer seeing players being able to nominate a world and move all their bases (or maybe 6 or 12) from another world. Everything tried so far hasn't, in my view, worked out as intended.