I'd rather not simply roll the dice on a rework from the present... trio(?)... of job devs.
If a rework could be sufficiently warranted, though, I'd like to take a core concept, such as Sin (in the sense of transgressing against assumed norms, moralities, or even metaphysics and asserting our own path and domain instead), and build around whatever ways that could fit with our blue, red, and black visual motifs from thus far atop the physical aspects unique to wielding a greatsword, likely with sub-themes towards those blue and red sides (perhaps red uniquely ignoring the mass of the blade for more rapid movements and blue adding yet more to it, etc.) with little if any fushia-colored muddling of the two...
It would also likely need a thorough examination of where its sustain should come from -- be that primarily healing or mitigation, or alternating between the two via some sort of resource system entwined with the aforementioned red and blue overtones / visual themes -- and intended procedural personality (how playing it makes one feel, such as direct/strong, tricky/bastardly, "big-brain", rhythmic or opportunistic, etc.).
Also, Guts is just a warrior. Every part of his identity we've also seen among WAR lore, from giving oneself over to the beast (Berserking), the self-sacrificing wrathful abandon aspects (which, in Berserk, depend on relic armor anyways), to even his move-set. He's a decently fun model, sure, but we're not going to get any more distinct a DRK if centering the job around him. You'd just get a Warrior with a sword.