Leadership need more fodder to facilitate what I'll coin for now "conquest campaigns". Essentially when leadership is taken that should give the PC a small band of fodder/followers in addition (or even in place of) the cohort. The cohort could be something left to the role playing aspect of the game where a character like the leadership's current cohort would have to be recruited in game with things like diplomacy, gifts / trade in services, etc...
I'll use a couple examples to make my point.
For the additional fodder/followers the leadership score would determine the number maximum you could have at any given time, and any lost take a year to replace. That number though would be substantially increased from where it is right now though. So that at 7th level the NPC fighter/rogue would chose to become a leader using leadership of a ring of bandits. the NPC would recruit people to work under him, and together they would rob people somewhere... The 7th level NPC who just got leadership would get something like:
7-1 X (leadership score) = 1st level fodder
7-2 X (leadership score) = 2nd level fodder
7-4 X (leadership score) = 3rd level fodder
7-6 X (leadership score) = 4th level fodder
Essentially its enough fodder to warrant a group of bandits, as the leader rises in leadership score and level the problem her presents grows. For PCs this is also how they would rise to move from being responsible for a hamlet to a kingdom.
The cohort would be nixed from the feat itself. If players wanted cohort types of allies they would need to be recruited in character. If the campaign went from adventuring to role playing out a kingdom for a while and participating in large battles then the PCs could do that, and if they wanted to adventure they could recruit "cohorts" to tend to their affairs while they quest for the holy grail or whatever.
I strongly dislike cohorts as in my campaigns they invariably get relegated roles like clerics and bards (just supporting the party not doing anything interesting) and they take away from the main action of the PC heros. They make combats difficult to manage as there are more initiative values to track and make declarations for.
I would personally like to see leadership scrapped. If the party get a cohort let it be a story reward, not a feat. Same goes with followers. For conquest campaigns the DM can award followers based on the party's actions, this makes it feel special to get followers rather than some merely some feat granted ability open to anyone who didn't use Cha as a dump stat.
In my campaign cohorts are banned from leadership feat and the party every few adventures gets a guest NPC who is controlled by one of the players. This has worked out really well and I feel it builds the party's connections to existing Good aligned NPCs in the campaign world as they fight side by side rather than merely having henchmen.