Can DU make another suggestion to Fargo for a Codex contribution? If we raise the money, a small ultra-isolationist monastery is inserted into the game. Upon discovering the monastery the player is told to immediately swear fealty to 'the old ways'. The player can avoid entering comat at this point by either a rather easy speech/charisma/whatever check, or (to the surprise of the players who choose it for the lulz) by choosing the token 'insult' response. Either non-combat entry to the monastery will alllow the player to wander and find out that the monastery is a group dedicated to something they call 'the old ways', who share the belief that these 'old ways' will once return (you get slightly more information if you chose the 'insult' response - for reasons that will soon be clear). The twist is that the player discovers that not only are the monks split into factions with conflicting ideas of what the 'old ways' actually were (hence why they respect a man who speaks his mind more than one who tries to sweet-talk, even though the latter will still avoid combat) but even WITHIN each faction their concepts of the what the 'old ways' were are vague at best. Even worse, large portions of each faction were either young children at when the 'old ways' existed (the monastery has discovered a means of stopping aging within the walls of the monastery and can slow aging somewhat even outside the monastery - teaching the player this latter ability is the main reward for working out the puzzles without slaughtering everyone, and it will help him save another NPC, maybe even a companion, from an aging curse later in the game), or entered the monastery centuries after the old ways ended, so their faith in the old ways and the 'decline' are completely dependent on stories handed down by their elders.
The player can resolve this in one of two ways (each of which gives the aforementioned reward). He can convince a faction that their view of the 'old ways' MUST be the right one, and help them defeat the other factions in combat. Or with a good speech/charisma skill he can convince them that what they need is some improved leadership system to declare an 'official' version of the old ways. The player can convince them of either of two means of government - he can say they need a King (there's two plausible monks that could manage the role, and their names must have the initials D.U. or V.D.) or they can use a Comrade system, where the monks democratically vote every decade on a committee to design the official version of the old ways (until the next election-by-Comrades).
If the player makes it to the King/Comrade solution, he not only gets the aging cure to save the NPC/companion later, but he gains the monks as allies and can drop in to trade for a peridocially updated inventory of mystical items similar to the tattoos in Fell's shop in PS:T.
Sounds to me like an awesome way of squeezing as much Codex in as possiible, while avoiding anything that would alienate/confuse non-Codexers, nor would non-Codexers see it as a silly in-joke (unlike the 'nameless' Deus Ex mod).
Edit: if the player fails the initial speech check (any player can get in using the insult dialogue option, and the speech check should be low enough so that only those who are going for pure combat-power, with little interest in solving the 'mysteries' of the game, should fail it) and ends up having to kill the entire monastery, his reward is that he gets to loot a very powerful weapon that will come in handy to those who just want to slaughter their way to the end, but is less helpful than the aging cure/info/mystical items/future dialogues when shopping with the monks, etc to a player who is taking the 'I want to work out all the game's mysteries' approach).