Very few people play unholy DKs, they crop up when someone sims them at the top of dps charts for a while and then most of them drop off the face of eternity. I was one of those people, I liked unholy, it was my first DK DPS spec, and I always thought thematically it was the most fun of all the DK specializations. However, I've always ended up playing other specs, since WoTLK there's very little reason to be unholy, when frost does everything it does better and easier.
Unholy is a very clunky spec, it's been very powerful in PvP, but for very bad reasons. It's an auto-fire option, you macro your stuff together, you pick your moment and you eat heals, while your pets murder someone, you get to concentrate almost entirely on control, because roughly 50-60% of your full burst dps is entirely automated. I don't think that's a good way to setup any class.
PvE tends to see fewer unholy DKs, because their ramp up time and general inability to do fast, on demand burst always hamstrings them. No raid bosses just let you sit on them and beat on them anymore, so if unholy does 5% more damage than frost, frost will probably in real performance, have roughly 10% higher dps, simply because of ease of target switching and a lot less ability to screw up.
Why I'm going over this, is that I actually think the current unholy setup, would work fabulously as a ranged dps class, since the clunkiness and annoyance of things like dark transformation, would then be offset by ranged capabilities and an ability to set up fights better, since there'd be so much less running around (it's usually not the melee who burst for 1 million dps at the start of a fight). Some abilities and mechanics would need to be modified to balance PvP, but I think DKs would be made a much more robust class with a ranged option.
The original DKs were casters, so if unholy is supposed to be the specialization in the vein of the WC2 DKs, with abilities like raise dead, death and decay and death coil at the forefront, why not take it all the way? Branch out the class, add more gameplay options. Plus DKs have felt kind of ignored, since we haven't even gotten a real tanking overhaul (Or well, a real anything overhaul in a very long time), this would be a great way to bring some energy back to the class.
I'd love to see my DK using ranged scourge strikes and whatnot, not to mention, there's just always too much melee :P