9. Boss Battles - Battle Other Assassins
Metal Gear's boss battles have always been the stuff of legend, going all the way back to Psycho Mantis reading your memory card on the PS1. For Phantom Pain they're few and far between, but the one that stands out most is against the dreaded Skull Unit; an infuriating superhuman combo that can outpace you at every turn. Honestly, MGS V can feel a little broken when it goes into full-on combat mode, but the idea of tackling enemies that are far more accomplished than yourself is one AC has dabbled in multiple times. Mostly, it's turned into one of the godawful 'chase missions' as you sprint after a boss character, waiting for the prompt to one-shot them in the neck, but AC III did see you tackling a mysterious antagonist in the present day timeline, whose close-quarters showdowns should've been fleshed out into a proper game mechanic. Assassin's Creed Rogue touted the idea of tackling enemy assassins as part of the story, but when it comes to gameplay, how awesome would it be to essentially crib from AC's multiplayer, putting you in a citywide space and asking you to track down an enemy of equal or accentuated abilities? They could hide in bales of hay, scout you just as much as you did them, blend in with crowds and everything else. It'd be a real test of your skills, and would absolutely be a major shake-up to the core gameplay formula we're getting increasingly tired of.