I'd like to chime in. I LOVE the idea of playing as the villain. Some of my favorite games are the games where you are the villain! Dungeon Keeper, Overlord, Dungeons, GTA (all the MC's are villains who kill, steal and blackmail, they just aren't as bad as the antagonists), etc. etc.. It's just all in how the story plays out. Frankly though, I think you need another reason for the MC to turn the town into his personal fortress other than it's the first place he stumbled in. If I was in his shoes, I would book it ASAP because it's the closest town to where I got into a fight with my old clan, and thus the most obvious place for them to search, making my confrontation with them happening well before I could even turn a quarter of the town.
I'm guessing you'll have the finale of the game involving the confrontation between the MC's forces and his old clan?
Now, I have to ask, is there going to be magic in the game? In many vampire stories, they aren't "magical" beings, but more along the lines humans infected with a virus that gave them what we could consider having super powers like super strength. So is your story going to have vampires being turned like in Elder Scrolls via like a virus that they can be infected with? Or is it going to be more of a "magical" kind of thing.
Also I don't understand why you have to "kill" off characters to feed on later on in the game. I can see it after he stumbles into the town after suffering a lot of injuries in his fight, and needing to recover his strength ASAP. But later on in the game I don't see the need, as a vampire's power generally doesn't come from how much blood he's sucked, but more along the lines of their cunningness and ingenuity.
Well, I think the problem having her as the "main girl" is the way you've described her (or at the very least how I view her based on what has been said so far, which isn't much to be honest). She's a vulnerable person you take advantage of and manipulate to get her to betray everyone she knows and loves. While she makes a great starting girl to help you take over the town at the start, a girl like that is also the one you have to keep an eye on because she could just as easily be manipulated into betraying you by your enemies. A "main girl" should either be someone who is unquestionably loyal to the MC, or someone who the MC sees as his equal. And a vulnerable person you take advantage of and manipulate, isn't exactly someone you see as being loyal or an equal, just someone you use. I know you said you want to make a 'toned down Harley Quinn", but there have been countless characters like Harley Quinn that were made before and after her creation that never worked. Plus, Harley Quinn is also one of the Joker's biggest weakness in his plans, her actions, or inaction in some cases, has been his downfall. And if the Joker was fighting an opponent who would have killed him instead of Batman, she would've been the death of him long ago.
If I have to say, instead of making her a "vulnerable" person who you manipulate into helping you, make her an "outcast", someone who was once apart of society who has since been ostracized by the town for something that wasn't her fault. Someone who feels like everyone she knows, everyone she loved and cared for, has turned their back to her and betrayed her. Someone who was so royally screwed over by them, she would have no issue seeing the town burn.
