Like focus on the Unlimited Blade Works route heroine ending, with Rin and Shirou outcome, but have Saber come to realize through Shirou that changing her past wouldn't really change anything and show some love between the two of them (maybe like acknowledgement that they love each other but content with just knowing that they do) (Stay Night), the whole twist that Archer is future Shirou (UBW), with Sakura going berserk with the Holy Grail's corrupt power (have them go into why its still like that even though Kiritsugu destroyed it) (Heaven's Feel), have Saber turn into Saber Alter (something like she fights Shirou and all that realization I was talking about frees the Grail's (Sakura's) control over her and she moves on like at the end of Stay Night) (Stay Night) (Heaven's Feel), Ilya become the new vessel of the Grail and after accessing her ancestor's memories she develops a plan to destroy the Grail along with Rin's and Shirou's help (Heaven's Feel), she sacrifices herself to save her younger brother (Shirou) destroying the Holy Grail (Heaven's Feel) and Rin saving Sakura (UBW), Rin and Shirou reflecting upon everything that happens and moving on with their lives for the better (Stay Night).