Going by the name of the Dragon Knights' attacks, they don't seem to do anything that slag walkers don't already do in some way.

The biggest problem with this suggestion is that it has little gameplay info. For the Dragon Knight, all you have are a basic physical description, attack names (not even full attack descriptions), item drops, monster type, a one-line story description, and the fact that it's only found in Tier 3. There is no information at all about its behavior, aside from what we can guess from its attack names. The Dragon Sword is even worse in this regard, only having a star level, a recipe, and flavor text. There is no information about its attack pattern, charge attack, damage levels/types, bonuses (if any), or even a physical description. You're going to have to fill in at least some of these details before anyone will even consider your suggestion.