The problem with having a world map with all the bases is that the map wouldn't have eneryone's bases on it even if the map wall was 500 blocks tall by 500 blocks wide.
But the hall with all the banners might be good as you it would be intereseting and would give a lore to people as they come and go.
I'm not sure suggestions is the best place for your post though, this is more for suggestions for the staff to implement, not for comunity projects.