Idea from warhammer 40k: Introduce a CBM that temporarily “shuts off” one half of the brain while allowing the other half to run, and alternating between the two - effectively eliminating the need to sleep at a minor cost of intelligence and perception when activated.
Imo a big disadvantage definitely needs to be inherent to such a device, as i cannot see it working flawlessly even in the future. More fun if it was in early development and problematic 
I’d nerf it by giving it a chance to modify stats semi-permanently
Say, 5% to lower a random stat by one, 1% to lower a random attribute, plus a flat reduction to health for every “switch”.
The stats will return slowly (maybe with MTTH of weeks?)
EDIT - Yes i agree with the post below me so i did modify it a bit, plus gave some explanation on my rationale.
jcd, in this case it’d be more effective to just eat (literally) some caffeine. It won’t be that much risky.
Neural AMP
semi high energy use, causes moderate pain. When it wears off you are dead tired instantly. Over use can damage intelligence.
Someone would have to rework fatigue first. Currently caffeine simply takes away fatigue, meaning you can avoid sleeping indefinitely as long as you’re hopped up on caffeine.
Could this be used to keep fatigue green as long as power stays on BUT with a chance to kill the player like stim overdose?
Let’s just discard the “turn off half the brain” concept, that’s just not a reasonable thing to do in humans since the two halves of the brain do distinctly different things. FYI: “idea from WH40K” almost automatically means it’s not going to fit in DDA. I personally like WH40K a lot, but it doesn’t mesh with the DDA setting at all.
The simplest thing I can think of that has a similar effect though would be something that simply applies a stimulant effect any time the player is above a certain fatigue level. It would only kick in if you’re tired, but when triggered it would steadily drain power, and you have the risk of stim overdose as per usual, because it wouldn’t bypass the code stimulant drugs use, it would just apply the same effect. Leaving it on would be risky, especially since if it’s automatic you aren’t going to get messages about being tired, your stim level is just going to keep climbing.