Would a swordbreaker that is scaled up to the size of a one or two handed sword be useful, or too situational?
I’m unsure if it would even be possible, or at the very least, useful.
The entire idea behind a swordbreaker is to have a parrying tool you can use to catch and lock up your opponent’s blade. So, you’d carry a sidearm in your main hand, this could be a sword, an axe, whatever, and you’d use the swordbreaker in your off hand, to parry with. These wouldn’t necessarily break the blade, but they would allow the user to torque it and keep hold of the blade, while retaliating with their own primary weapon.
A longer, sword sized, swordbreaker would much harder to produce, and much more fragile, which starts to undermine its intended use. The two designs that come to mind off hand were comb style blades, which could hook and catch a blade between the teeth, and two pronged, “forks.” (I’m including trident daggers under this, if anyone is wondering.) I suspect making a sword length comb would result in an unreasonably fragile item. Too fragile for use as a swordbreaker.
Extending a fork to sword lengths would be similarly pointless, because you’d still only be using the six inches near the grip, and the extended tines would just get in the way and slow you down. Someone could make one, but I doubt it could be used, at least not as a swordbreaker. I’m also not even considering the structural stability on a long fork, because, really, it wouldn’t be able to work as a swordbreaker.
There are examples of existing swords that include sword breaker features, such as tines designed to trap the opponent’s blade near the guard, though these features are more common on parrying daggers. You will also, sometimes, see heavier piercing blades, like the estoc described as swordbreakers. This is technically incorrect, as those weapons were designed to deal with armor, but the term is used that way sometimes.
So, no. It’s not even a situational consideration, just a practical use problem.