I'd design something ambitious. A combination of VN and open world FPS-RPG gameplay. It will be Sci Fi + Horror + Fantasy + Psychological and will take place in the year 4036 in a world that suffered 3 apocalypses. There will be 3 protagonists: 1 male, 1 female and 1 more genderless creature (that will be unlocked after finishing the first two stories). The art will be 3D-2D cell shading and will resemble Huke's art. The OST will have great variety from Pop, to Metal to Electronic to Hip Hop. It will have time travel, alternate worlds, reincarnation story elements and a time loop subplot. The female and male protagonist will have romance between them in a route called "The abridged Sunshine". The last route called "Blaze of the last apocalypse" will have an epic conclusion that will make the fans go wild. It will be scored 9.90 on VNDB and many gaming sites will give it a perfect score, and everyone will praise it.
I just came up with all this just now. Forgive me if it was too unrealistic to actually make it happen; I always like to imagine things like that.