Stamina has been a game breaker for me in any Mount and Blade mod or medieval game, for various reasons, the most important being immersion. Having to constantly look over and see how much stamina you have left really breaks up the flow of combat, which is thee most important thing imo.
Mount and Blade offered players a semi realistic simulator for how medieval combat would have felt, and the adrenaline we get from playing is nothing compared to what the actual soldiers would have. There fore adding a stamina system completely defeats the purpose of what your game is trying to offer, a very niche experience to a very small player base worldwide.
We ( at least I ) didnt buy Warband for its rpg open world elements, and i certainly didnt buy it for its graphics, i bought it entirely for the combat system. Other games have tried, but Chiv and Wotr, dont even come close to that Warband feel. This may come as a terrible shock to some of you, but swords, shields, armor, etc, these are not nearly as heavy as games like Chiv and Wotr make them feel. And hopefully you arnt looking to attract those players. That would not be a good look.
You have a nice little player base already built up of people your game is perfect for, medieval enthusiasts!
Please dont turn us away with stamina systems and what not, we are talking about grown ass men, fit mutherfuckers well adjusted to the weight of their arms and armor. YOU may not be able to swing a sword for 25 mins, i dont wanna play as you tbh, i wanna play as a knight, who totally could!