Horizon's Despoiler is a good one.
Firstly, the Despoiler isn't terribly cost effective. Two Devastations are better and cheaper. So if the Despoiler were to be slightly upgraded then that's no biggie.
Anyway, Nate, what you've missed here is that while the proposed Despoiler gains in its extra broadsides it loses in the removal of the 4 prow lances. The current Despoiler could potentially fire a 7 lance salvo, with 12 WB offside left over. Now it can fire 10WB & 3L (10WB offside). It keeps the same amount of total AC, so no difference there. Less total firepower, just a clearer role (sit back and go broadside). Faster and more powerful than an Emperor, but more expensive and lacking the +1 Ld. Also agree that the Devastations lances should be reduced to 45cm range.
As for suggestions for new Chaos ships, well I've often been disappointed by the Chaos heavy cruisers. One is sadly overpriced (Styx), another is based on a cruiser that I dislike (Hades) and the last, while balanced, is really undergunned for a heavy cruiser (Acheron). I have made several heavy cruiser variants and would like to see one of those become official. The Hecate is much as described in the blurb in one of the BFG Mags, i.e., a heavy Devastation. The Charon is a heavy Carnage and the Cerberus is loosely based on the Slaughter. I would post the stats for them, but they're on my other computer which is currently in storage.