Not exactly what I was thinking but that is a good idea to resolve the letting him go free pathway which is the only one that I didn't think of resolution for, so I like it. I imagine that when defeating Titus your options will be to kill him, free him, or transform him and keep HER as a slave
For who would play Tatiana I always pictured a blonde, off the top of my head would probably be Bridgette B or Britney Amber (to really highlight the bimbo you made of her, and she hates what you turned her in to) or Lorelei Lee (for a meeker Tatiana as I think that shiver she does when she plays scared is awesome at denoting how terrified "Tatiana" is of you). Though I suppose that if you wanted a red headed Tatiana then Penny Pax would highlight the submissive bimbo you have made of her.
As for implementation imo this will be either you kill Titus and have his skull in your room (no transformation) and can get a bonus stat at midnight by drawing power from the skull (you choose either willpower, intelligence, attractiveness or fitness) just prior to falling asleep or you transform Titus but trap him inside of a time rift, everyone else will think he is dead and only you have access to her (this is the only way I could think of that wouldn't require a massive rewrite of weekly events to include what Tatiana is doing throughout the week though I admit pimping her out also crossed my mind) essentially it will be one extra scene that happens at midnight where you you would pick a stat and get a bonus to that stat after sleeping with Tatiana, you would pick to either trick Tatiana to give you her power every night in exchange for you saying your trying to find a way to get her out of the time rift when in reality you aren't doing anything, she will half assume your tricking her but cant do anything about it because she has no other options and she is always looking forward to your visits as she has no contact with anyone other than you. Or you can make her suffer more as she suffers from being lonely and then you force her to give up her power to you.
example of Trick pathway:
Tatiana: your back, you were gone so long, I was so lonely
You: I told you I would be back, are you going to be needy again, maybe I should just go.
Tatiana: No, I'm sorry I will be good, ... Did you get any closer to figure out how to get me out of here, I have been good haven't I?
You: Well I'm a little closer but Its still going to take a while Babe.
Tatiana: you are really looking in to it though, your not just going to let me rot out here.
You: I'm hurt by the accusation, here I am busting my butt trying to help you and this is the thanks I get?
Tatiana: I'm sorry, I'm sorry I shouldn't have doubted you.
You: you know me having to come all the way here is really making things hard if you want me to keep coming back here you have to make it worth my while.
*Tatiana starts to Undress*
You: well yeah I will take that too, but I was talking about something that could actually help me, it will be good for you too, I mean your power is just wasted out here but I could used some of it to help you get out of here faster.
Tatiana: you mean it, if I do this you this again you will really get me out of here.
You: as soon as I can, the more power you give me the faster I will be able to find a way out of here.
... *sex scene with a chosen stat upgrade.*