I could just customize the handle of a K-bar, but I would ponder the sturdiness of the bronze knuckles connected to it.
I am thinking that may just be the EASIEST way to go instead of creating a whole new knife.
I could just add a sharp peg on the bottom of the handle, and build the knuckle covers into the handle.
I also came up with a REALLY crazy design that would require quite a lot of engineering ingenuity, but that I think would work pretty well.
I tried to address several problems that people commented on about brass knuckles, or trench spikes in general, how it would be hard to drop them or get out of them if you had to.
I also was thinking about an idea of having a "disengage" bracelet to go with the knife, it would be attached to a pin in the spring locking mechnism that holds the knife up by a peice of elastic twine that if you stab something and let go and pulled away quickly, it would disengage the spring, pulling the knife in and unlocking the knuckles, but then I realized that if you hand was stuck in the brass knuckles you couldn't exactly pull it away to disengage it.
Overall its a pipe-dream and requires a lot more ingenuity than I currently have, but I think its built on sound concepts, and if not tactically sound is at least "cool". (Come on, how could the bastard child of a switchblade and brassknucles NOT be cool?