I remember playing Deus Ex: Human Revolution back in 2011, and remarking on how well the mechanics could work in a multiplayer setting if tweaked and rebalanced. Now that Deus Ex: Mankind Divided looks to be doing those very same rebalances and improvements, I really hope we see a multiplayer mode added to the game.
Once again, the game's setting offers perfect potential. With A.R.C., Task Force 29, the Illuminati, and the mysterious hacker group, there are four different factions at play. On top of this, the game has three combat-oriented playstyles that all could work well in a multiplayer setting: hacking, action, and stealth.
Imagine it like a mixture of Aliens Versus Predator, Bioshock 2: Fall of Rapture, and Watch_Dogs. Team One has a hacker who opens access to vents and turns on a remote controlled turret he/she can control from the console. Team Two has a stealthy player who uses the vents to sneak behind lines and take out the hacker. A combat focused player could shoot the stealthy hacker, but then be taken out by Team Two's hacker patching into Team One's turret. It's a perfect Rock-Paper-Scissors effect.
The controls and mechanics are also highly fluid and intuitive. Stealth takedowns could work great, but can only be done if you aren't in a player's line of sight (excluding if you're invisible). Combat takedowns can be done at any time, but leave you vulnerable to being shot -- just like hacking. Items could be looted from your opponents and the environment. The quick select wheel/bar lets you easily access your inventory on the fly. Energy bars keep everything balanced, and encourage using augmentation sparingly.
Levels could actually include lots of twists and turns, and the variety of locales available means each could be visually distinctive. Leveling up would unlock augmentations and other new gameplay options. Players would get at least one loadout for each playstyle, which they could swap between lives. You'd also be able to use any equipment found mid-match, regardless of whether you'd unlocked it yet or not.
The original Deus Ex had a popular multiplayer that even got a Human Revolution-themed mod way back. So let's bring it back in full force, even if some of the fanboys will cry "I NEVER ASKED FOR THIS".