Not sure if it's possible, but an augment that would show vulnerable areas on mobs that can be targeted for additional damage would be cool. Maybe activated by having the target in your crosshairs for a few seconds. (With some sort of scanning animation playing during this.) Toggleable. I'd say brain slot more than eyes sine it would need to calculate the most vulnerable spot.

Another augment could be one that shows the probability of hitting a target with the current weapon. Sort of like a HUD V.A.T.S.

Maybe with both equipped it can show you both statics for hit in general, and how likely you are to hit the weak spot.

not sure how this would translate into minecraft, or mod compatibility in general, seeing as you're asking for weak spots on monsters, which is difficult to do.

I do like the idea of showing Hit statistics, which would probably just be stuff like "Attack Speed, Dmg, max DPS" and such, since the HUD is a bit underutilized IMO, but that is a far cry from a V.A.T.S. from fallout.

Maybe a combined value that registers as a "Threat level" maybe taking into account current armor, weapons, and augments.

I'm pretty sure that Immersive Engineering implements some kind of headshot system with it's revolver, so it's somewhat possible. With my suggestion it would basically tag an enemy after a scan. There would be a limit to the number of actively scanned targets so someone doesn't go overboard. Maybe 6. I feel like that's a good number.

iChun's Dismemberment mod might be useful for this