For a game of Cyberpunk 2020 I want to build a villan with a pair of cybernetic tusks who can function as Cybersnakes, effectively making him a cybernetic walrus-man. The problem is, the rules on the Cybersnake are very unclear: they have to be installed in "any orifice greater than one inch". Would the mouth qualify for this, and could they replace the upper canines? Or do they indeed need to be stuck in a one-inch orifice, like the ears or some of the holes lower down on the body?
1. You are the GM. Tiny quibbling rules like this are not things you should let stop you from designing an AWESOME WALRUS MAN.
2. Houserules are a thing, and it's not cheating to allow something in an edge case like this especially if you would allow it for players. Justify it in-world with a genius cybersurgeon if you feel you must.
3. A good rule of thumb for NPCs is 'would I allow this for players as a houserule?' and 'would I allow this for players as a houserule if they went on a minor quest?'. For recurring villains, you can even say 'would I allow this as a reward/result of a major quest?'.
4. Ultimately, as long as you consistently apply the rules to both players and NPCs, you are answerable only to verisimilitude - whether or not it makes sense in the universe. In this sense, it surely does - cybernetic robo-tusks surgically implanted in the mouth is perfectly reasonable in a cyberpunk setting.
AWESOME WALRUS MAN