In my honest opinion...the biggest problem with Deus Ex, HR and MD, is that using stealth, to be more specific, stealth takedowns is punished by the game's energy system.

A takedown, Lethal(L) or Non-Lethal(NL) take energy. No matter if the enemy is Alerted(A) or Non-Alerted(NA). In any other stealth game, when you takedown an A or NA enemy, there is no penalty. It is considered your reward for remaining undetected and getting the drop on the enemy. Just for instance, Dishonored, Metal Gear, Splinter Cell, Hitman, some of the biggest names in stealth, have never required a specific "power meter" in order to silently takedown an enemy.

However, in Deus Ex, you are simply punished by an energy bar in order to silently takedown an enemy. Why? In the game, you have access to weapons, Tranq Guns, Stun Guns, Pistols, etc. All able to silenced and takedown enemies with absolutely no penalty. With these, you can also takedown enemies at a distance, without having to even move. With a Tranq gun for example, you can literally sit behind cover and clear an entire room, 50 ft away, with zero penalty.

So the argument, that without an energy bar system, the game would be too easy or OP is simply untrue.

My suggestion is simple. There should be 2 types of takedowns implemented into the next Deus Ex game. Stealth Takedowns and Alerted Takedowns. Stealth takedowns are on NA enemies. You are playing silently, taking out enemies who have not detected you. There is no punishment for taking them down, NO ENERGY cost. Next, Alerted Takedowns. These are takedowns on A enemies who have spotted you/are aware of your presence. They have their guard up and will need more force to be taken down. These takedowns REQUIRE ENERGY.

Stealth Takedowns - Time does not stop(Energy is not used) : Alerted Takedowns - Time does stop(Energy is used)

Now keep up with me here. Stealth takedowns would be simple, simple chokes(NL) or throat slashes(L) which would keep in line with NO ENERGY and be silent. Alerted takedowns would be super aggressive, like the ones already in the game, the spin flip and punch(NL) or the double bladed stab to the back/chest(L) et

This way...the game does not punish you for playing stealth-fully taking down enemies one by one, as long as you remain undetected. If you break stealth, you can use takedowns, but now they require energy. Pretty simple isn't it?

One more note to the biggest tired argument against this:

*This is not a spamming "free-kill button"...Remember, energy free, stealth takedowns can only only be used on un-aware enemies. Walking/Running around will alert enemies and not allow to spam an area with takedowns. Unless of course you use the silent AUG which will then use your battery which ruins the argument entirely.