Yes, but unless you're a certain type of caster Charisma doesn't do much heavy lifting in the standard set of things. All the other stats tend to impact the game more directly and much more frequently.And, think about it. Charisma is important for leadership sure, but so are wisdom, and intelligence. Casters would inherently have better ability to apply leadership through raw attributes and direct power, yes, but they get less "perks" because of all their emphasis is placed in personal power and learning instead of leading and command most of the time.
Also, from a fluff/lore standpoint, I see Charisma as being far and away the most relevant stat for how you relate to and are viewed by other people, which is what Leadership is all about.
There are a couple options here- if you want you could make it Charisma plus another stat, of you could have other stats be relevant to attracting a certian kind of follower (since Charisma affects overall numbers).
Or you could rescale the chart and have it go from 0 to 100 instead, and include everything except the kitchen sink, such as your character level, charisma score, your ranks in certain skills, your total net-worth, the size of your fortress, your alignment, and any other factors the DM wants to throw in.
I mentioned before that I wanted to split up the cohort and the rest of your horde. I thinks this will help to emphasize that your followers are, for the most part, not really suited for combat on your level. Not unless you want to get a lot of people killed really quickly. It doesn't even have to be against a high CR enemy like a dragon or demon or something. Largescale conflicts between two opposing forces of low-level characters could have a very high mortality rate.
In general I don't know exactly if or how I'd rescale the chart for followers- probably so that you had fewer, but higher level, followers, so you could actually set them to doing things that had a more definitive impact. If not individually then at least in small groups. Right now you'd have a few followers levels 4-6 doing everything important and 100+ guys carrying dirt or harvesting wheat or dying like rabbits against wolves if you sent them to fight anything larger than a housecat. Given their low stats and poor skills even spreading your name and message probably wouldn't get them very far- they'd be the guy on the corner with a sandwich board screaming about how the world's gonna end tomorrow. Not very attractive for potential converts.
Essentially there's to many of them and they aren't good enough to bother micro-managing.
As for the cohort, I'd make that come in 2 separate feats almost entirely unrelated to Leadership. For lack of a better name atm I'm just gonna call them Feat I and Feat II, and I suspect they will be light on the prerequisites.
Feat I gives you a minion, who is a Commoner NPC equal to 1/2 your level. The slightly derogative term "minion" was chosen intentionally, because even if you upgraded the HD on the Commoner a bit (which I think is perfectly fitting, given that a standard humanoid gets a D8 as a racial hit-dice) he is basically ****. He's dead if he gets anywhere near combat, and is really only good for minding the camp, running errands inside a city, and maybe helping put your armor on or sorting spell components. He/She exists primarily to be a spare set of hands and to do the things your adventurer is to important to handle himself, like cooking, digging ditches, or hell, even providing comfort and companionship on cold, lonely knights provided that doesn't grosh the rest of your group out.
Your minion draws a nominal salary, something like 10 times their level in gold pieces per month. Trivial for an adventurer but a very good wage for a commoner, which explains why there is are always fresh applicants despite the appallingly high mortality rate.
Feat II upgrades your minion into a cohort, who has PC-class levels and is equal to 2/3 of your level, which is about the point at which I'd set the HD for an animal companion, to make sure that people know it's a class feature. There are a couple different options here, and you can pick basically anything that you DM approves and fits your needs and theme.
Combat Medic- pocket Healer
Occult Researcher- Wizard/Archivist
etc etc etc.
*obviously using the RAW base classes would lead to some wild disparities in power here, but we already knew that; I'm working under the assumption that all options you are allowed are equally powerful and valid
The cohort is always 2/3 of your level, acts like a totally normal character under your control, and is equipped with 20% of your cut of any loot*.
*these values where pulled out of my arse, and can be modified as necessary; I just wanted there to be some drawbacks to this obviously very appealing pair of feats
So basically, for the cost of 2 feats and a gold-tax, you get a second character to play as, albeit one who is slightly squishier than normal.
The biggest benefit here is that it would allow smaller play-groups to fill in anything they might be missing from their normal roster. For example if their DM tells them they need a skillmonkey but no one wants to play a rogue as their primary character, they can still get one.