Have a rolling dictionary maintained at leisure by the builders. Let people suggest slang words for common words. Enabling this will randomly replace your words with slang ones based on their race and citizenship.
What.
Eh...not ideal to me.
Pass.
No.
The game had tried something similar, where it took your input and manipulated it. Due to playability and the loss of roleplaying opportunities, and backlash from the players, the staff removed that feature. In fact, the game has added additional features to overcome language code.
There is nothing stopping you from doing it right now. It shouldn't be codified.
How about a 'slang <x>' command where you can enter either a normal word or a slang word, and receive the inverse? 'kank' for 'fuck', etc etc.
This just doesn't seem like something that should take up coding time when a player can just... do it themselves.