Personally, I don't know why I need to mention this. It just seems like something everyone is doing these days. Far be it from me to not be fashionable. Are you okay with this?
Currently in Dragonhead Charisma is "the ability to think fast and say what needs to be said to entice others into doing your bidding." That's a powerful little statement, but notice that it says - entice - and not get. It means that charisma encourages people to do your bidding. It does not command them. It's not a charm spell. They can still say no to whatever you are asking. In Dragonhead you also do not use your abilities. Instead you describe what your character is doing and your abilities are tested by it. In the section on Hard & Easy it mentions that there is no limit to how hard a check can be.
Infinitely hard = Impossible.
Certain things cannot be done.
Of course, the first time a bard encounters a guard you know all of that is getting chucked out the window as the player says, "I use my Charisma to cajole my way past the guards." The DM will say, "Give me a Charisma check." The bard will roll high, possibly even a natural 20 and the DM will say, "okay, you cajole your way past the guards." And the rest of us will yawn. Because it's boring. But that doesn't matter because often we play to get our way. A lead pipe may be crude and heavy and clunky but if it works then it will be used over and over and over again.
Now what if there were no Charisma ability? Nothing to roll the dice against? The bard could still say, "I use my Charisma to cajole my way past the guards." But the DM - now without Charisma to reflexively ask for a check of - would have to ask, "okay, so what do you tell the guards?" To which the player would either have to dig deep and come up with something that might authentically allow them to slip past the guards or come to the general understanding that guards are guards and not to be easily slipped past.
If you have heard this before it's probably because you - like I - watched Professor Dungeonmaster's video on the matter of getting rid of Charisma.
Wherein he very charismaticly makes the case for getting rid of Charisma. I don't totally agree with him (when do I ever totally agree with anybody? :-) especially since this is Dragonhead and not D&D. A large part of the game centers around the DM listening to what the players have to say and branding it hard or easy before the dice are rolled (each hard puts a -2 on the check, a triple hard idea will suffer a -6 etc). Unlike Advantage/Disadvantage there isn't always a chance that you might succeed.
The big problem with getting rid of Charisma, is that it's always been there. In the OD&D book Men & Magic, Charisma is the only ability to get more than a two or three sentences about prime requisites. Of course, Charisma in OD&D is more about leadership. It's about followers and loyalty and whether your character will be killed when captured. I am pretty sure there is nothing in there about using your charisma to coerce NPC's, especially since OD&D doesn't even have ability checks. However, Charisma has changed over the years, rising from dump-stat to do-everything stat. How annoying is it going to be for the DM to encounter that moment where they might have called for a Charisma check but now there is nothing. What will they do? Listen. Imagine. Play it out in their heads and wonder if it would actually work?
You're asking too much! I shouldn't have to think! That's like playing a game of dodge ball where you actually have to move!
People are going to resist it. They'll blame the game for not playing like D&D. They'll go back to playing what they've always played, content with the knowledge that there is nothing better out there. Of course, if you make your game exactly like D&D then what's the point? Go play D&D.
There is also the problem of Charisma being an actual thing. It does carry weight. There are charismatic leaders and charismatic used car salesmen, both very skilled in the art of leading people to do things they may someday regret.
(And who doesn't want to have these guys on their side?)
Seriously though, watch this clip and think about how funny it is and yet how boring it would be if all the salesmen did was walk around the lot, meet potential buyers, roll the dice and either make a sale or not. In many cases that is what Charisma gives us. Certainly there are exceptions out there, players who just don't play like that. Yet it's the rules you put in the book that set the baseline for how the game is played, not the exceptions.
So it's a tough call.
In the end, I can't say whether I will keep Charisma or not. I admit that I cannot look at a character sheet and not notice it missing. Still, it seems as if there is much to gain and little to lose by giving Charisma the boot.