So, here's an important question, what would the goal of Leadership be? While I get that getting followers to heed your command and help you out in combat is nice and all, its hardly should be the only thing that having authority and command over others should allow you to accomplish.
A few days ago, I forgot where, but it was on this forum, one thing I noticed was that brought up was in a sense a lack of "downtime things" for noncasters.
Casters had lots of personal power and magic to do things like conjure elementals or make magical defenses for their bases for instance.
Meanwhile, what do non-casters do? What do you swordsmen do, aside from making sure their muscles are in tip top shape, while waiting for their wizard buddies to complete their new staff?
One of the goals I think we should do in a total revision of leadership is to actually give non-casters the option to, if not get more personal power, get major political and military power.
And then, have said power be available and applicable to the adventurer who takes it.
Part of that be might actually removing the "Followers" or "numbers" system in place of the orignal leadership which defines how many people serve under you and their level (remove because such things are hardly worthwhile keeping track of and really need to depend on the situation and type of leadership you're going for). It should be replaced with some other mechanic to encourage martials to use it over casters, though I am not sure which.
Tell me, Deep Blue, what should be leadership's tangible effects in your idea?