Most people in Known Space don't like cybernetics and regard those sporting them as freaks and wierdos or worse. The interfaces available for use with computers at higher tech levels are pretty good, holographic controls, data gloves, display visors, and having chips wired into your brain looks like a very nerdy affectation for little actual gain. Trying to hide cybernetic devices is also frowned upon by most governments. The only reason you would want to do so was because you were up to no good, and security forces tend to assume anyone with implants is a spy or terrorist until they prove otherwise. Cybernetics are also expensive, dangerous and and frequently lead to mental illness.
'eff off tinface!
As well as the modifiers by tech level on p38 of the Monggose Traveller Cybernetics books, add a -1d3 DM for degree of cultural bias against cybernetics and a further -1d3 if there has been a recent incident on the world involving a cybernetically enhanced criminal, spy or terrorist. Then give a -1 DM for every 3 Law Levels the society has – the higher the law level the greater the paranoia about crime and subversion and the more dangerous a cyborg is in the popular imagination.
Prejudice at its mildest level to a flat refusal to allow the individual to enter a business premises or home due to fears of covert surveillance and people assuming that a cyborg is mentally ill. More serious negative reactions may involve local toughs offering to fight the cyborg in order to prove that real men are tougher than half a man, local police forces taking a more violent than usual line with cyborgs committing misdemeanours (That metal oaf is littering – wait is he dropping a nanobot spy thingamajig? Shoot him!) and concerned citizens calling the cops on the spot.
On most worlds a special ID can be granted for those who have had implants for legitimate medical reasons, which can defuse most cases of prejudice. Others demand that cyborgs who have had elective enhancements have a day-glo orange tattoo, especially those who have concealable enhancements, so the public know that they are under serious danger of being 'gargoyled', recorded and monitored against their will.
'Ah, the anaesthetic is wearing off. You may feel the urge to scream...'
As well as the survival roll on p35, make a second roll at -2 to see if there are side effects, with an extra -1 per implant/improvement already possessed.
These may be constant pain from badly joined nerve endings, infection, feedback from a new implant disabling another, Parkinson's disease, Tourette's syndrome, outright implant rejection resulting in failure within 1d6 months, losses to INT, EDU and DEX due to general brain and nerve damage. Each operation and type of enhancement will have its own particular pitfalls.
'I am afraid your legs are illegal in this colony. Please report to the special customs agent, the guy over there with the oily overalls and the hammer drill...'
Plenty of states outright ban elective cybernetics and put severe limits on the capabilities of medical cybernetic implants. Weapons as part of a cybernetic implant are treated as one category higher with regard to laws relating to arms. It might be OK in a jurisdiction to have a concealable handgun, but not if it is so concealable that it springs out of your thigh or shoots from your wrist. Concealable cavities are also frowned upon, and many jurisdictions will insist on them being welded shut. Higher law levels will have strict laws about recording devices and dmand that memory chips be removed from enhanced eyes and ears and their wi fi blocked. Really nasty ones will wave these things through, but put hackers on the job of putting viruses in the software to monitor the cyborg and shut down the implant if law enforcement deems it necessary. And what goes for entering a state goes double for entering a corporate enclave and quadruple for government and military offices. (Yes sir, you may come onto our airbase, but only if you unscrew your head and legs).
Bow puny meat-things! I am Mechanisto the Great!
This is the big bugbear. Any talent beyond the human norm seems to result in some eccentricity as a side effect, and gaining that talent through messing around with the brain and nervous system just makes those eccentricities more extreme.
All PCs have basic sanity of 11+1d6. Modify this using the table below
For each 10% body mass replaced by cybernetics -1
For each extra skill level gained by cybernetic means -1
For each stat point gained -2
For each moderately superhuman ability (high speed, UV vision, armour) -1
Modification directly affects brain -1d3
Major deviation from human body plan (weapon, wheels instead of legs, grav units etc) -3
A roll under sanity must be made after every additional cybernetic modification, and at the GMs discretion after every traumatic experience the PC meets during play.
Failure results in the acquisition of a behavioural quirk. Roll d10 on the table below +1 per existing quirk, and repeats make an existing quirk worse.
1 Mild megalomania. I am just better at this than you thanks to my machine parts. -1 on all social skill rolls.
2 OCD. Any failed task must be repeated again and again until it is done right to achieve machine like repeatability and perfection.
3 Clean freak. Must keep cybernetic bits clean and in working order. Roll vs Sanity on exposure to dirt or freak out about malfunctions and infection.
4 Paranoia. THEY don't like cyborgs. They ARE out to get me. -1 social rolls.
5 Paranoia II. The computer is jealous of my humanity, the robots feel threatened by me.
6 Depression. Oh why did I do this to myself. I am a freak. -1 on all social rolls.
7 Mania. I can do things a million times faster and more efficiently than ordinary meat people. Look! -1 on all skill rolls, -2 on social skills, roll vs sanity or become aggressive if fail in a task of contradicted.
8 Existential paralysis. Is this real, or just an input from my machinery? Roll vs sanity in any crisis situation or dither unable to work out what is actually going on.
9 Schizophrenia. Temporarily lose touch with reality. Roll vs Sanity every hour to get back online.
10 Schizophrenia II. Lose all emotional affect, cannot feel or express emotion. -2 on all social skills.
11 Mild psychopathy. Total lack of empathy, see people as machines to be used and manipulated with appropriate social inputs, feel no embarrassment of fear. +1 social skills.
12 Major psychopathy. Who or what the hell are these gibbering meat puppets? -3 social skills, save vs sanity if opposed or become homicidally violent.
13 Megalomania. Who the hell are these sacks of slime? I am great! Automatically fail all social rolls, save vs sanity at -2 or use violence on anyone who fails to agree with your godlike superiority at everything.
14 Extreme Paranoia. Get the bastards before they get you. Fail all social skills, kill all humans in sight if fail sanity check at -3 (and robots, and let's chuck in the cyborgs just to make sure).
15 Catatonia. Endless paradoxes, feedback loops, depression and weltschmerz. Totally useless, cannot move or think.
Removing augments gives a repeat sanity check to lose a quirk, but not all reverse operations will increase the sanity score – you can't put back brain cells that have been flushed away to make room for a microprocessor.