hmm i haven't done anything to complex with ren'py before but think the menus are something that could be do-able especially if you're familiar with python! tho i'm not too sure if it's still ideal. i think the contradictions could also be done as well--maybe storing an array of decisions made and comparing these further along the line if x decision is made check y index to see if it's a contradiction--just a possibility. looking forward to see your solutions!
I think I'm going to do something along those lines. I'm going to make a system to alert a player when a character's statement is suspicious (the AI has a sort of built-in polygraph) and then give the option later on to choose which suspicious statements to question. I haven't decided yet if I'll then require a player to present proof that a statement was a lie, or if just questioning the right statements will be enough. I want to see how complicated it turns out to be to implement.