Doing evil things in bioware games tends to make your character seem schizophrenic, but if you're happy with it and Morrigan is evil enough for you then I guess the request is invalid?
How is my character schizo? Because he did some morally questionable things while at the same time working to save his country? How would he benefit from being King of a ruined country? How could he be the hero and sit on the throne of a wasteland? Why wouldn't he want to strengthen the Wardens, an organization he is commander of? In Origins, you can flat out not be a nice person from the very start of the game. That doesn't mean you're gonna be a complete moron and get yourself killed and country destroyed.
I don't see the request as invalid. Some people didn't experience the relationship with Morrigan because she was cut off to female wardens, I also think my evil power hungry couple play through worked because he was a Cousland. Also, Morrigan didn't challenge the Warden as much, unless the Warden wanted to be good all the time. I think some people are tired of the whole "Fix me I'm broken" LIs which we had in Alistair, Leliana, Zevran (sort of), and then the entire DA 2 LI cast. Mixing it up would be nice.