This is a very interesting concept indeed. It would of course completely depend on the context of the fight, the personality of the NPC and your own reputation. An honorable knight will never surrender to an ordinary bandit or cutthroat, and will prefer going down fighting to being at the mercy of some lowlife.
That all depends on your gameplay choices though. If you spend your time doing legitimate mercenary jobs and build up a sizeable fame and following doing so, you will have a different impact on someone than you would as a hedge knight or something of those sorts.
Imagine you encounter someone at the fighting pits in an encampment in the woods. They claim to be the most valiant and skilled warrior in the entire province, and challenge you to a duel. According to your fame and gameplay style/choices, they will know/not know your name and be incredibly cocky/ humbly ask for a duel. When you're having the upper hand, the warrior will continue fighting until the end when "your fame does not precede you". They refuse to surrender to some stranger without a memorable name. Winning this fight, and thus killing the warrior or completely incapacitating them, will result in you getting a lot of fame, which will make future duels to turn out differently.
Let's say you approach the same situation, this time having built your reputation as a freelance knight beforehand, winning tournaments and battles all across the lands. The warrior will approach you rather than you approaching them, and introduce them with a lot less attitude. Nevertheless, you still fight the warrior. Should you be very close to death, they will show their mercy and end the duel, complimenting you on your fighting skills or saying they thought you were made of tougher steel. Should you be on the upper hand, they will surrender. As a legitimate freelancing knight, you are expected to honor this warrior and his cries for mercy. Ignoring them and finishing the warrior off will result in a change of your reputation. However, should you be known as a ruthless mercenary, killing the warrior despite his cries will not result in the same dent in your honor.
Should your fame be plentiful enough and the situation fitting, the warrior could offer your their services, either for money or for the glory of battle. Should you choose to deny this offer, they would still remember the mercy you gave them, and come to your aid should they ever catch you fending off a small group of bandits and looters.
I'm not sure about the implementation of an actual real-time "intimidation/threatening" feature in-fight. An emote-like menu would ruin the immersion for me, and a hotkey which triggers a voice saying "Surrender now!" doesn't really seem like a viable option, considering the general atmosphere of the game, much less so a text balloon with Comic Sans. However, if something like a gesture could be done, that would be nice. When an enemy is tired and injured, standing quite far away to catch their breath, you could hold your sword out, pointing the tip straight at their neck. They would go down to their knees and drop their weapons, and you'd be given a choice of some sort.