In November, Cristyn came up with a game we call Magnate. We have played it at least twenty times since, revising the rules substantially. I have written up our current version.
Unfortunately, it requires lots of parts in addition to the Decktet: a six-sided die, two ten-siders, and lots of tokens. I worry that this might be too much for a Decktet game.
Although the game is for two players and is clearly inspired by Settlers of Catan, it is not much like the two-player Settlers Card Game. If anything, it's a port of the original Settlers.
The rules are different in several nice respects, though: Rather than continuing until one player gets a target number of victory points, the game ends after the second time through the deck— this can definitely make the endgame a race. If you can't build anything on your turn, you sell one of the cards from your hand— so you never have turns in which you just can't do anything.
I haven't created a wiki page for it yet, but I thought I'd post about it.
EDIT: OK, we changed the name of the game. It had been called Sovereign Power, which seemed a bit misleading.