I might try this! I probably wouldn’t try something commandy like you’ve got there, maybe something more like the flavor of this, but if you want to let me know how to do it… well, there’s more chance I’ll do something than if you don’t! (What I’m trying to say is, sometimes I don’t manage to follow through on projects, but I’m interested!)
@matt w, That link is pretty cool! It’s a fun little experiment with a story-in-a-font. My approach is similar would be a little different, revealing those messages only after a specific sequence of letters.
I’ll be sure to poke you every once a while to see if you’re still up for this 
I’d prose writing all the lines in a text document (Word, Google Doc, .txt file, anything will do really) and use a | character to mark where the key ends and the secret begins:
Take red key.|You have taken the red key.Small update: I tried to hack a small adventure together with this system, but ran into limitations pretty quickly with the “replace key-text with key-and-secret text”. This replacement is meant for just a couple of characters, not for long form text.
And alternative approach can still work, by using ligatures. This would simple be “replace key-text with an image”, where the image traditionally is another (pair of) letters, or an icon. I might give that a shot.
Do keep us updated!