I could see it working for an officer, but I actually had notes on a separate officer as a different career because I see it having a few specific combat powers as a member of the military
What about a police officer who commands cops in combat? A biker gang leader with savage charisma? One of the things I appreciated about Modern was there was no need for classes for everything. All those classes could be represented with a dose of Charismatic.
and the Negotiator has more bolstering powers.
There's something to be said about bolstering troops in combat. For instance, if you're being pinned down by fire, sometimes the best solution is to rush forward and shoot the bad guys, rather than hide under cover. If Modern had a good pinned gunfire system (it doesn't), a Will save to rush forward and shoot back would be appropriate. But most characters (including physical soldiers, like a Tough/Soldier or something like that) would likely have poor Will saves. Inspiration to the rescue; it gave save bonuses too! (And said soldier need not be an officer, they could be a sergeant or other NCO.)
As for the mob boss or a cult leader, I think they would be the career that focuses more on Intimidation as a focus. Mob bosses don't really inspire their subordinates as much as they browbeat them and prove they are tougher to motivate them.
D20 Modern is a cinematic system. It makes putting on a headband and using Flying Kick as useful in combat as shootin' them up. A boss should be able to contribute in combat in some manner, and I don't think just looking cool and being threatening is enough. (That was also covered by Frightful Prescence.) Some mob bosses (I'm not talking
top bosses here) could and did lead their troops in combat. Lucky Luciano did so before he became the head of the Gambino crime family.
I guess I'm saying I don't think it's necessary to try to make a class for gang leader and cult leader and X leader and Y leader; if you give the Charismatic class the tools it's supposed to have, the more flexible system can handle almost any PC or NPC type the player or GM cares to draw up.
Cult leaders break down their followers and brainwash them into action, but there could be some kind of inspiration power there as well.
For an adventure I ran which took place in the Middle East, one group of bad guys were called "cultists". Naturally any GM modifies an adventure they run. I "promoted" these cultists to heroes and gave them the Faith talent. I also replaced one from each group with a leader who had Inspiration (and also Faith) but generally weaker combat stats. Both NPC types had pretty lame attack bonuses, being not optimized, but between Inspiration and Faith they were scary dangerous. I suppose these "cultist leaders" were combat chanters, or maybe you had a very specific definition of cult leader. In any event, these guys were definitely combat leaders... and they were
not competent military tacticians, so I don't think any kind of military officer class would apply.
If you go back and see where I posted the first draft of the Charismatic and the Con Artist, maybe you can offer some suggestions because I am still on the fence on how they panned out. But personally I see inspiration as more of a career focus then one for the general Charismatic. I'm not sure what I have in there is generic enough, but that is where I am going for this project.
I downloaded the .doc. I don't know what general power level you're looking for compared to 4e DnD, but the Inspiration talent itself seemed pretty weak. It's an encounter ability that only gives +1/+1 for a single round, and that's all the inspiration you can give out per encounter. There are cleric at-wills that are as powerful as that, or to look at it another way, the warlord's buffing encounter powers come with damage, but since the Charismatic is not a fighter, the buff has to "make up" for that. (The abilities that allow dazing opponents are much more reasonable, for instance.)
I would suggest making Inspiration a power (one that you can choose, rather than having it a generic class ability). A Charismatic con artist might not find Inspiration useful at all (unless they're a leader-type too like Nate Ford, and even then I don't think I've ever seen him lead anyone in combat). A biker gang leader, on the other hand, would find that much more useful. I would also suggest either giving it a bonus worthy of an encounter power or making it an at-will.
A more combat-leader-esque class might have an ability like "Fire On My Laser!" which would be the ranged equivalent of the "Lead from the Front" ability the hobgoblin commander has. (That trait gives allies +2 to hit and damage on anything the commander hits in combat.)