The terrain would represent the 2D document while various 3D units would work on the terrain to write the document.
Some of the units could be bots (e.g., an AI bot to update the introduction in real-time as the rest of the document changes, etc.) while other units could be your human collaborators.
Units could work on the document concurrently in real-time and a 3D view would show them working much as they would in a real-time strategy game.
What if we took it one step further and somehow modeled a more complex business endeavor as the "map" and interactions with the game elements effectively issued real-world orders to the team, sent emails, invoked AI, etc?
I am thinking something like a 4X game UX where you complete an entire B2B webapp integration & consulting package over broader timeframes. Not just writing one document. The whole saga. All participants can log into this "game" and "play" it. Certain participants may have different views or capabilities depending on real-world org roles.
Being able to visualize strategic elements of an abstract business domain in a gaming-style context might be a new thing that warrants deep exploration. The user interface for RTS games allows for rates of interaction and decision making that I have never seen with any other style of computer interface. The UX loop around an FPS is marginally faster in absolute terms, but the complexity managed in a typical RTS/4X puts it into the dirt by comparison.
Just watch someone using GitHub issues vs someone playing SC2 in a semi-competitive stance. The energy difference is extremely obvious. Clearly, doing serious business won't ever look exactly like someone managing a photon cannon rush, but I think there is definitely a spectrum here we can move further down.