I see you guys not trusting MR and I wonder, would you say no to a Watch Dogs themed Pokemon GO style game? Hear me out:
Imagine you're in a train or a bus, and your phone lights up with a notification. A potential hacker like yourself is in the area, and you can now engage in a competitive minigame like the hacking in Deus Ex HR and MD but obviously better (and there should be a variety of these minigames). You win, and so you earn XP and scale up in a Most Wanted leaderboard in which only people from 50km around appear. Being up in the leaderboard makes you more likely to be attacked, and visible to others, etc etc.
There would be mechanics for defending your mobile phone from other hackers, like setting up traps and whatnot. This core PvP gameplay would then be fleshed out with more events and missions etc.
I believe the problem with Mixed Reality is not related to the tech but to the design of the games themselves, as Pokemon GO proved.