Depends on your writing and direction.

A hive type mosters would have creation as a force a power.  those with the most people win.

then there taking control of another force.  love taking control of the destruction force...  i love my mom, you called her a name now i punch you in the face.

bad example im at work and all, but you can kind of see it... kind of... ok maybe not

I think you have hit all the major ones,
the only other thing i could think of is not quite a power but it can be used to impose your will on the world around you.

Deceit.

physical deceit:  I have the bigger army(Bluff)
Financial: i look like a millon bucks(just looking the part gets you in the door.)
technological: i steal, hack, ect... you tech.
Information: Blackmail
Social: conmen

just a thought

In a world of Wizards, artificer, and alchemists I cant see gun powder working.  I think someone would have invented it but it would not be practical.  A man would have to buy a warded gun.  His bullets would need to be individual warded, or a pouch to put them in warded.  It would suck to have only 6 bullets in your gun and have a wayward sorcerer exploding your gun belt.  As wells as it being doubly expensive.  You have to have the materials to make the gun powder and the materials to make the wards.

I think the idea of a gun make sense, it’s a wand/rod with a handle.  As well as bullets being ruined projectiles that can have different functions.  Lighting, force, fire, etc…  the cant misfire or explode because you stand up to a wizard with enough power to by-pass your guns/bullets wards.  the cost would be just the spell placed on the gun to make it throw something fast and then the type of bullets you want. 

Of course the above would only work in a place where magic was common, or common enough to have a artificer in most city and towns. 

Not sure how common-place magic users will be yet, but for the most part they will augment normally existing professions. For example, a Blacksmith is still a blacksmith with all the normal tools of a blacksmith. Having a Fireslinger or an Earth/Metalslinger around to help you melt or shape the metal would be the same blacksmith with more high-tech equipment.

when I read this i get the feeling of guilds, Blacksmithing guild that sends out people to populated areas based of strength of magic/tech/skill.  these blacksmithes need to send money back to the guild via "stage coach"  (think ponkerton trains in the old west.).  just a thought

Glad to help 

Another thing to consider is faith magic. Religion was very prevalent in the old west and in many towns was the most fortified building so that the villagers could fall back there in times of trouble.

I could see a lot of potential for a old powerful priest bustin out the whoop ass when the sh**t hit the fan.

That reminds me of this old Zombie moview were the presit bust outs come kung fu and yells "I Kick A$$ for the Lord!"

First I want to say like the idea, and I totally get where you are coming from on the questions and if it can work.

I was working on something similar.   The idea was what would happen if magic had always been around and it was modern day.  I like the idea of trying to explain what was item of technology would never have been made and what could have happened if we had the ability to sling energy around.

So when you ask your questions here is what I had sitting already in the back of my head.

1)   Can you have a self-defined "Swords & Sorcery-Western" story without Firearms of any kind or is the self-description of a "Western" require Firearms to be present? Would you as a reader be let down by picking up a story describing itself as a Western without any guns or gunplay in it or could you be satisfied with it being replaced with Chanbara-style swordfights?
I would say yes, and here is some way.  Why was the firearm created.  To give a weapon to a solider that could penetrate armor/shield and was relatively easy to train with.  Its why we stopped wearing mass amount of metal armor, well until our tech. got good enough that we understood the way bullets moved and Kevlar was invented.   So in your world would a gun ever be needed if you had wizards running around.  Could an Artificer simply have created a wand/rod or other type of weapon that the mundane could use and act like a gun.  Lots of books and movies bring up wand duals, and I think this would work great in a western setting.
Then you brought up the melee combat and still have strong Gun/wand play.  Ways to keep this going, would be to find a reason why it is.  Could be as easy as wizards or talisman can put of a shield that stops the wand energy from getting to them, but it is a lot harder to stop a sword in the gut.  Or limited amount of charges in the Wand/Gun.  If you have a wizard that can stop a few blasts of gun or wand fire, might be  nice to have a sturdy sword as a back up.  Or spell eaters, maybe a race or group of people that are like an anti-mage or can absorb energy of spells thrown at them but a nice dagger to the back works well.  Lots of ideas on that reason.

2)    What options are there to do the classic Western trope of the Fast Draw at High Noon with a Main character is a Wizard of Ill-repute, not a Swordsman?  Similarly, there's the classic scene from a Fistful of Dollars/Yojimbo where the Man With No Name proves how badass he is by killing a bunch of guys in a matter of moments in a fast draw. How could you do that iconic scene with a Wizard other than *Raise hand* *Fireball* *Done*?
I talked about wizards wand dueling above, I think this would just take it to the next level.  I see spell slinging a lot like the old western duals. 

Hope this helps

Rading your blog on saw Dionaeahouse...
thanks for that.. great read