This^
Adapting Tsukihime straight-up presents too many problems on the series composition front alone. Routes are too incomplete by themselves and some aspects are too mutually exclusive to properly mix and match. I'd love it if it were told as a "Shiki route" where there is no main heroine. It could be seen as ripping off the way KnK presented the question of whether or not Ryougi was the murderer, but the payoff would be very different and it'd only mark the beginning of the story.