Okay, I appreciate people trying to make this one work. I do get why too. In fiction, the Grim Reaper scythe is a very popular weapon. It has fantastic visuals and it looks wicked. When it comes to fictional weapons, the author has to make a choice of how fantastical they want to get. I’m a fan of understanding the reality because the more one knows then the easier it becomes to make what I want work. There is really no real way to make the traditional farmer’s scythe practical and realistic as a battlefield weapon. It is too heavy, too slow, due to the size of it’s head, it would need to be fairly short in the haft to make it more wieldy. However, the biggest kicker is going to be its limitations in terms of movement and the greater amount of time it takes to actually hit someone.
If you’re going to run with the scythe, then it becomes a hewing weapon or a weapon that cuts. Puncturing or stabbing with it is a deep dream that allows one to hook around into the perfect position to hit the other person.
In order to properly strike, the scythe must come across or the wielder must be off center to stab it forward. This is a problem, as while it is possible to strike across, most polearms function on a grid that allows for diagonal cuts and forward strikes. The blade tip almost universally points toward the enemy in direct line with the shaft. This allows it a greater attacking radius and more lines with which to attack the body. It also allows the polearm to be used within smaller, more narrow spaces such as courtyards and castle hallways. It can make the most of smaller, tighter movements, rather than big ones. This saves energy for the wielder and allows them to fight more quickly.
The scythe, meanwhile, points away from the enemy. The point comes back toward you. The long curve wraps back around. This is actually important because it means that the blade must travel a greater distance before it reaches the enemy. It also must travel further than all the other polearms in order to connect. Due to it’s shape, it’s strengths actually come from hooking around an opponent because that’s where the greatest force will be in terms of cutting. Even if you put a blade on the other side, it would be difficult to achieve the necessary rotation to create the force needed to hew or cut through an opponent.
For a hand scythe like the kama, this isn’t a problem. It’s much shorter and much more wieldy, capable of moving on different angles without sacrificing defense. It’s response is much more quick, and you can use it to hook body parts or sword blades in a way one cannot with the much larger scythe.
The short answer is that no matter what you do, the shape is awkward for polearm combat. It would be a dueling weapon only as one would have difficulty using it in formation, having a greater chance of hitting their fellows and their enemies. It would require a fair amount of space to wield due to the shape of it’s blade, thus becoming more likely to be stuck on walls or trees or in a random passerby. It’s designed to cut grass. The horizontal strikes would leave the wielder far too open and, more than that, they’d run a greater risk of missing. The blade style reduces the weapon’s reach advantage. The reach advantage is crucial to polearms, being able to hit someone else while they can’t close to hit you is one of the main reasons why one chooses to carry a polearm. It cannot, really, even marginally function as a puncturing weapon. It can’t really be used from horseback, though the greater curve itself is used for swords like the sabre and scimitar that are better capable of making use of the rotation to greater effect due to their shorter length.
It’s defense is also shot due to the limitations on the blade itself being entirely stuck on one side of the haft and the greater swings necessary to achieve even half the effectiveness of similar weapons.
Unless it has mystical properties, it’s just not a very good weapon. The problem is not where the blade is, it’s actually the shape. In choosing it, one is choosing a subpar weapon from a selection of similar types. Those weapons are designed to be weapons and they have a specific usage/function in mind.
Here’s a demonstration of the Jikishinkage-ryu Naginata. This is mostly for a basic understanding of striking patterns with a glaive type weapon. And the 2014 All Japan Women’s Naginata Final. I think this one gets easier to grasp when there’s a better understanding of how polearms were used, even just in a dueling type setup.