I want an It Follows slender-like horror game. You get the whole unstoppable supernatural being following you, but like in the movie, it's slow. It never stops but it's slow. And the area in which you can travel should be the entire world basically, like Google maps. You'd play it from first person, traveling across country, city, wood, mountain, whatever.
You'd have stamina and sprinting, limiting your ability to just outpace It, and whatever vehicles you can acquire will eventually run out of gas. Cities would have the advantage of easier access to supplies and vehicles, and npc's can help you, but they can also hinder you ( such as getting arrested by police for stealing a car, leaving you a sitting duck in a jail cell ) and the fact that It shape shifts means it can come at you in the middle of a crowd and it'd take you by surprise. Countryside/woodland/tundra/mountainsides would be devoid of human life, meaning you can see it coming ( if you look in the right direction ) a mile away. But have fun dealing with the local fauna, as well as issues of starvation and exposure.
Sleeping would be a risk, you can choose to sleep certain hours, provided you can roughly calculate in your head just how far you've gotten from where you last encountered It, and how long it would take a human figure to travel a certain distance. Even if you've left a continent It will have 24 hours in a day to get to you, meaning you can never stay in a place for too long. Add in environmental and npc hazards which can injure you, make you sick or deprive you of necessary money, supplies, etc. and you've got a serious no win scenario.
A horror game based not on alertness and quick reflexes but on mental stamina and careful planning, that's what I want this game to be.