Non-Combatant Characters

There are definitely stories which need a main character who is capable of fighting the fight and doesn’t need any diplomatic or other less martial skills. There are many, however, which are fine without it, too. Many of those stories get a strong fighter where a smart speaker or a stealthy thief could do just as well. Non-combatant main characters can be interesting to explore and offer a whole host of new plot points to use that would never work with your regular fighting-form hero.

There are a few genres where a fighting-form hero is not only the default, but also a necessity. You won’t get a proper action movie without a hero who is ready for all that action, obviously. And while you may play the ‘Greenhorn in the West’ trope card in a western movie or novel, you will eventually get them up to fighting-form because the genre demands it.
On the other hand you have stories which almost never feature a fighting-form main character. Romance stories are more focused on emotions and drama than on fighting your way through a horde of enemies. Political thrillers are building the tension on the manipulation of people, not on the ability of the main character to kill twenty enemies before breakfast.

It is said that if you only have a hammer, every repair job will look like a job for that hammer and that is true — you need a full set of tools to have the right one to apply to any repair job to do it right. The same is true for characters.
If you have a fighter or a group of fighters as the main character(s) in your story, every problem will be solved with fighting, either directly (against enemies) or indirectly (by only offering tasks that need fighting to be done). Every time your character(s) get into trouble, they’ll draw their weapon(s) and get down to killing or at least disarming enemies.
If your main character(s) or at least the most major one are non-combatants, though, they will have to find new ways to solve a problem. Violence will not do. They might have to talk people into letting them pass where a fighter would merely draw their weapon. There might be a tense scene in which they sneak past a gaggle of powerful guards who are looking for them. They could look around for another way to where they need to go or find out whether there’s another place to get what they’ve come for to this one.
There’s more than a hammer.

Another way of having a main character who is non-combatant and still get in all those sweet sword duels or shootouts is to have them have a bodyguard. Instead of featuring the fighter as the lead character, make them a backup for the lead character.
In a way, that happens in the 1999 version of “The Mummy” — it is clear from the structure of the movie that the main character isn’t Rick, but Evie. It’s her actions and decisions which drive the story and she is the one who is responsible for the rise of the mummy in question. Rick is her bodyguard. Rick is the one who in the climax takes on Imhotep and gives her the time to find and read the right lines to turn Imhotep mortal again. He gets to kill Imhotep, but it would never have happened without Evie’s actions. Evie is a librarian, not a fighter, but Rick is a former soldier, so fighting is how he made money in the past.
Not only does the bodyguard give you the chance to work in some of those sweet fight scenes, it also opens up new plot lines. What if the bodyguard is captured and the main character is suddenly on their own? What if the bodyguard betrays them and delivers them to the enemy? What if they fall in love with their bodyguard? The potential is endless (well, almost).
If you need or want all those fights, but want to have a main character who is not into them, a bodyguard might be the answer.

If you decide to use a more ‘fight friendly’ genre and want to go with a non-combatant, one of the biggest questions to ask yourself is ‘what can they bring to the table instead?’
In a noir detective story, your detective might be less of a fighter and more of a talker. They might know a lot of dangerous people and be able to hire or borrow muscle for when they need it. Or they might be sly and sneaky and avoid being attacked by not being where they’re supposed to be. They might also be very fast runners — until their luck runs out.
In an ‘old west’ setting, the non-combatant lead might instead be making friends. There’s no need to fight the ‘locals’ when you’re friends with them. There may be no need for a shootout when the main character can prove that the owner of the biggest farm paid those cattle thieves for stealing from all the other farms. Yet, for that to work, the character needs to have the right skill sets and the right traits.
I’ll admit that I can’t see a way to use a non-combatant in an action scenario, although it might be possible to construct all action around someone running and hiding instead of fighting.

When you plot a story, you can go about this in several different ways. You can already have a main plot in mind and build everything else, such as characters and setting, around that plot. You can have a character in mind and build everything else, such as plot and setting, around that character. You can also have a certain setting in mind and then go looking for the plot and characters that will go best with it.
If you plan to use a non-combatant character, you will most likely be building the plot and the setting around the character. In such a case, you can easily leave yourself a chance to make sure that the character can survive all possible conflicts they get into. That can take the shape of the conflicts being social or otherwise non-violent, but it can also take the shape of a bad-ass bodyguard to protect the main character.

The next time you’re looking for a main character for a story, consider a non-combatant. Even if you don’t go through with it in the end, it might still give you a new insight into what you could include in the story that is not bound to the main character being a fighting-form hero.