Initially it was said to clog their respiratory system but in later stories they developed a more allergic reaction, with even gold coins fired from sling shots proving to be lethal. This makes them much more vulnerable and more than a little ridiculous.
When confronted by Cybermen most player characters will seek out a source of gold. It can be handy to have an obvious solution but compare this to how most players would react to Daleks. Daleks don’t have a similar vulnerability so become more intimidating.
By removing their weakness to gold Cybermen become stronger opponents. They still aren’t invulnerable, with weaknesses that any organic beings might have, combined with the vulnerabilities of a machine.
Attempts to clog or dissolve their breathing apparatus is certainly a legitimate tactic but should be no more effective than trying to suffocate any enemy. Their metal bodies would make attempts to electrocute them or use magnetism to immobilise them.
One attack that has been used several times is targeting the Cybermen’s emotional inhibitor. In ‘The Invasion’ this was used to send Cybermen into a blind rage, turning them against their allies.
This assumes then that the Cybermen don’t remove emotions, just restrict them. Those with the right technical skill could in theory trigger certain emotional responses, such as anger, sadness, happiness and even love.
If the player characters over use this technique or it just doesn’t fit the games master view of the Cybermen then there are other ways that the Cybermen could remove emotions such as by surgically altering the brain.
Alternatively the Cybermen could learn from their mistakes and make the emotional inhibitor better defended. It would also make sense for the Cyber Controller to be able to reactivate compromised units.
If the Cybermen don’t physically remove emotions, just inhibit them, then this raises the possibility that they still have some use for them. Could there be situations where having a Cyberman with emotions would help them understand their enemies or act as a diplomat?
Returning to the idea that Cyberman can be a very diverse race there is not reason that all of them would share the same weaknesses. If they regularly encounter attempts to suffocate them maybe they’d install back-up respiratory system should the main one come under attack, or even internal oxygen supplies.
There could be a small number of Cybermen who aren’t linked to the main network, whose bodies have low levels of metal on them and otherwise don’t have the same systems as the rest of their number.
Their job would be to remain isolated so that they can carry out repairs on the main units should they be compromised. They could repair programs, fit new parts and otherwise act as a mix of medics and engineers.
It would also make sense, give the races drive to survive, to keep a small number of Cybermen prepared to escape and start again, should things fall apart. This would consist of a craft staffed by a number of soldiers, a secondary Cyber Commander and Planner. All of which could stay in stasis until an emergency activated them.
The Cybermen’s ability to go dormant is a very unique ability. Like vampires they can entomb themselves and wait for centuries before emerging. Finding a tomb should chilling but the scarier thought is that there maybe more that haven’t been discovered.
It would make sense for Cybermen, if they have the resources, to establish a tomb for sleeper agents as soon as possible. Any planet that the Cybermen have passed through or held might have one or more tombs, waiting for the right circumstances to activate.
Upon awakening the Cybermen might attack directly or, if limited in numbers or outnumbered, operate in secret and slowly capture and convert others. By the time the locals realise why people are going missing it might be too late.
This adds a surprise element to the Cybermen. Player characters might be on an alien planet that has been there for hundreds of years only for them to discover a large Cybermen force resting beneath a major city.
The existence of parallel Earth Cybermen raises another nasty idea. The creation of Cybermen might be inevitable for all tool using species. They could come into existence on hundreds of different planets, spread throughout space. It could certainly be argued that the Daleks are just another form of Cybermen, using machinery to shape and change their organic bodies.
Would these different Cybermen fight or join forces? What if a powerful species, such as the Time Lords, began to adopt cybernetics, putting them on the same path as the Cybermen?
By removing Mondas as the sole source of Cybermen they become undefeatable. No matter how many you kill, how many of their ships and tombs you destroy they will always rise somewhere.
As long as a organic beings fuse themselves with machinery the Cybermen will return.