So, you guys know why you're never going to get these types of LIs, right? Two reasons: Gender-gates and Voice-Acting.
The resources used for making LIs are limited, as this is not a Romance sim. The developers have chosen to use those resources to focus on orientation, so different RL orientations have LI choices. Back when we had really dark LIs, we didn't also have LGBT LIs. so they could afford to make divergent Alignments in there companions and Romances, but at the cost of Gay and Lesbian LIs.
With fully Voiced companions in cinematic cut-scenes, you now have a staggering amount of resources spent on making Companions. Which means less Companions. How many Companions are recruitable in Baldur's Gate? 15? 20? A lot more than either Mass Effect or Dragon Age ever had in any case. And that's because the Voice Actor was able to squeeze all his voiced lines in like a 30 minute session at maximum. Modern Bioware characters have hours of voiced dialogue each. It behooves them then to make companions that the majority of their player base won't instantly try to ditch. Since most people actually play good guys, well....
The end result is self-evident: Zevran and Morrigan are your "darkest" companions to date in DA. A charming assassin, and a vile harpy caustic "social Darwinist".