T4R. For me, it would be a Deus-Ex: Human Revolution - esque game, but set in an open-world - Basically a cyberpunk open-world RPG.
You could travel across the world to realistic bustling urban cities with all the detail that Deus-Ex had in it's relatively limited city hubs. Level design in Deus-Ex was brilliantly non-linear - they never shoe-horned you into any specific situation; there were always multiple paths to traverse through any given space and a choice of sneaking past or going Rambo on hostiles. That kind of detail would be almost impossible to replicate on an open-world scale, but if it ever does, I would pay through the nose for it.
Also I want a high-speed motorcycle chase through New York where you can jump on pursuer's bikes with an elaborate hijacking animation that ends in you kicking them into the Hudson.
-
You're a good dude, Euler. Great to see someone else appreciating Deus Ex HR. You pumped for Cyberpunk 2077? That might be one of your nearer bets coming up for the game you described. For me, the ideal game looks like a cross between Witcher 2, Skyrim, and Dragon Age. I loved the Witcher 2's storyline and it's writing and voice acting felt beyond almost every other game I've ever played. The texture of the world itself was just terrific, too, it felt like a real place people lived and the characters were fantastic. Take the open world of Skyrim, now, with the exploration, the detail, the length, and the size. Add the level of intimacy you can gain with your crew in Dragon Age and that sort of company system. If I'm really dreaming, I'd throw in a Total War element of management, open battles, conquest and so on. I suppose what I'm looking for is a high fantasy world where you're in charge of your own mercenary company, making decisions about where to go and what to do, having your own personal adventures, etc. But it all would have that central plotline with compelling characters and writing.