You've had a number of "edition changing" plot elements lately, and I'm not sure I'd want to see something that leans on the fourth wall that much for
Tsukihime, but I'm also not sure how/if that would ever get cleanly incorporated into or acknowledged by the Works. It would be ambitious, and probably interesting, but the uncertainty around the developing plot changes seems like you'd risk contradiction if you venture too far outside of the relatively small amount of established new canon, which might be a difficult constraint to work with. Could be risky, but I'm certainly not against giving
Tsukihime a chance to shine, and the "murder mystery" concept seems like it fits better thematically with the darker flavor of
Tsukihime relative to
Fate. Also, you've done pretty well in the past with slightly-outside-canon speculation (
Trinity Vlad honestly aged really well, imo). I can definitely see why you're floating it as a possibility, but it's really up to you whether you want to do that much finagling.