Hello there, winaled!
It's my pleasure if my comment could encourage the developer further (>w<)/
Reading that Sinek acts as the final boss and somehow means that encountering (even killing) the others at the end means the safest and true winning..... I don't know how to react to this wicked scenario :'D (well, at least she suffers at the other routes *devils laugh* )
As for any recommendations or suggestions... I have a few ideas actually. I don't know if the content in the list had been discovered by you, but oh well here I go with my simplest explanation...
1. The game played in The Room. I think it would be easier to consider the kind of game they would play then you can decide the system, but that's my preference; you can design the system first then continue to polish the character and choose the best game that suits the rule of the story/system.
Anyhow, I assume that True Odds favors the gamble type of games or casino. I am no expert of those, but I suggest Craps (as the gamble system, guessing the number of the dices and the place of bets, is rather simple), Poker (well, the betting is kinda predictable and there are many computer system to run it and predict the result, as long as the players isn't hundreds of people. I know the struggle in programming that into vn later :'D ), Roulette (the play is also rather simple like Craps; bet your numbers, let the misfortune decides :')) or even Russian Roulette! (not just with regular gun, but also using different kind of unpredictable weapon for every player's turn! ...just how evil can I be? :'D ).
Or, you could use the cards with the already set-up rules. But this once, use ALL the functions of the cards, or as I said in my first comment; this time the player could choose which cards are ommited at the beginning. That could give enough variations or combinations of outcomes to each characters fate...
Oh, or it could a racing bet in which the characters use their deceptions to make sure their bets win the race!
Or, Truth or Dare bet or modified Werewolf cards game ; in which each players use their own tactics to accomply certain mission written on a card or dare by another, manipulate certain Truth from others to their advantages, or punish the one who is detected lying....
Then, it also an option to use children games; such as snake and ladder, monopoly, labyrinth, or even Musical Chairs with killing intention for every song played o_o
I just suggested some of known games; about the bet, "how the normal rules of the games could be twisted into", the penalty, and the prize of course could be as sinister as the team of developers want to ;)
2. The Room system. It can be a "you lose/win once, you are out" or decided by the sums of collected state/points from the games. (a) It could be only one room but with different kind of games for each turns, and the games have their own rate of difficulty. (b) There are some Rooms which divided into three or more type of difficulty, with each their own games and opponents; like Room AAA for easy one, Room 666 for Absolutely Dying In Here, etc xD
3. The characters roles. Honestly I hope that the gender or personality (or at least the reason MC comes to join The Room) can be variated, but oh well my contemplations are => (a) you could use the same Ace of cards personification again in the same room, or they could be "The Boss" for their own separated room and their own favorite choice of game. (b) Or it can be entirely different characters with different quirks at all, inspired from other games or folktale or myth! (c) Other ideas. for every different rooms or different type of games, MC will meet with different pairs of opponents. (d) At the entrance or before Ismet appears, MC have a choice to build an alliance with another characters to help him/her in any kind of level or type of game or Room he/she joins, no matter they meet in the same room or not later. Of course, with certain "commitment" will be paid at the end of the bargain *devils laugh* (e) Ismet is one of the players *sudden collective gasps in The Room* or at least the final boss, or at least appears on the screen, ha ha...
Last but not least, thank for the consideration after reading my mumbling lines of thought ^^;