Metal gear solid is a huge game and pretty influencial as well. I think it would be really neat if there was a referance to metal gear inside the game.
My idea for a referance would be this:
Whenever you type a single exclamaintion mark into the chat, it will instead display a red version of that butterfly indicator. A referance to how enemies in MGS have a red exclamation mark above their heads when they are alerted of you.