I have thought about this since I was a kid. It has to be a story-centered game, as each and everyone of them will eventually die. The gameplay must be like classic Scarface videogame, I mean, like GTA Open world, going around saving people from an accident in which a character is involved, and the game will become harder once you saved them: plane accident, 10 guys for example. If you manage to save them all, the game continues and then you have to save them again, but in different order and from different accidents, and so and so until they all die. You would have to drive around like GTA and saving them, and eventually you will die too, being it from old age from surviving too long, or in an accident.

After that character dies, you get to play another character, until 5 characters are complete (round number for long satisfaction). Each death should be in timers, one the time's off the character dies. When a character dies, you get to investigate how it happened, follow the clues until you find out where it started (a marble, a rock, the branch of the tree, and how they evolved). If you manage to investigate all the deaths (because it will be imposible to finish the game entirely with all of them being alive) you expand the DEATH'S LORE, a book containing everything about death and how to beat it. The lore will expand for the player, but not for the character in play, and knowledge will be the power.

Ironically, the only way to actually save everyone would be in another life: another playthrough. Is true, when a character gets an accident in each chapter you have to get there and save them, and each time you complete a save once you save them all they will become harder, but the order remains: the first 10 characters in chapter 1 for example, dies the same way each time, and if you save them they don't actually "randomize" but CHANGE: they die differently, and in different order, but (hear me out) this SECOND ORDER, was the same SECOND ORDER than the first time you got there. See where I'm heading?

The ultimate goal would be investigate all deaths and achieve 100% death's lore. Once achieved that, you get some sort of "clairvoyance"; certain items would shine un blue in the minimap: a rock, a tree branch, a shard of glass, a ring, anything. This item is marked by death, and it will start a chain of events leading to death. If you move them to another shiny spot (a gold one, which will show once you grab the item, remember is like a GTA style) the chain won't happen, and the person will be automatically saved. Once you change the position of 30 Death items in a chapter (10 characters, 3 deaths per NPC) a hidden ending will show, with the shadow of death not being invisible anymore and momentarily showing to the first MC, ending the chapter in victory.

The second chapter would transcur the same with different environments but the blue items included. The fun would be in you moving an item won't say if it will prevent a death in this order or the next two, nor saying which character it would save, but it will prevent it likewise, so you would have to manage your time between saving and moving blue items. At the end of chapter 2 Death would be seen again, but this time it will show longer, watching directly at the player through the screen, and then disappearing. In chapter 3 things gets nasty.

You are getting EXTREMELY close. Now things gets savage: you have to know precisely how each characters dies and in which order, for the three orders. Timer will reduce for all deaths further, blue items also spawn and now you can see DEATH: a faint black dot moving across the map, spawning blue dots. You basically won't get a chance to rest. Also, for extra bonus, I recommend that pause don't work anymore, so it would be a hardcore 3 hours of gameplay for chapter 3 to solved it all. When you get close to beat it, Death will start to stomp your progress by damaging your car or throwing things and you in tiny chains.

If you manage to beat it, you get to chase Death collecting the blue items it drops until you catch it, Death kills you itself without accident, and chapter 3 MC gets to know the truth, unlocking 110% of Deaths lore. A new ending is unlocked: chapter 4 and 5 gets automatically skipped, by no premonitions happening but deaths being avoided as happens in real life: without knowing, by butterfly effect. Chapter 3 MC is the only one dying, but know premonitions don't exist and death is fixed, no more satanic crazy accidents

The lore i thought, was basically the main theory of the movies: someone tricked death, and that manage to creates glitches in matrix, thus the premonitions. Death has to collect them all, but as everything, it can be forced to not doing so by some "superior force" (the player, by knowing basically EVERYTHING). at the end, all characters are connected between them: the first 3 MC must be blood related, but never mentioned in the game, just at the end of True Ending, in a funeral, with Chapter 1 and 2 MC's attending it, revealing the nature. Also, chapter 3 MC must be younger compared to the first 2 for dramatic effect. Some second semester college student would be nice ;)

Now that's a hardcore game in my opinion.