I would say the futuristic Negh'var variants that we see in the beginning of the VOY series finale 'Endgame' as the ship has two large weapon pods beneath the wings. Through those pods the ship could have a unique and hi powered dual beam/cannon that is similar to the special cannon on the Galaxy-X.
A Negh'Var that has the same skills as the Galaxy-X would be nice but not unique like the Galaxy-X is. Think about it this way, that ship is the only cloaking ship the Feds have, it gives the biggest advantage to line up your attack to any unsuspecting opponent over any Fed ship.
Now what would give that unique feel to a Klingon ship? Combat cloak or maybe some kind of interphase cloaking device (it is canon).
when it opened fire with its main guns it sent a wall of shots as wide as the neghvar that shut down all of ds9
add extra universal slots and give it 2 permanent bop escorts or maybe a way to knock out all cloaks in the area for 10 seconds at a time with a 2 minute cooldown