I always knew Act X was going to have a heavy Katie influence; I spent a fair amount of time looking at how to weave her story into the game.
One idea I briefly played with was to make a small stand-alone game (loading the same savegames to retain player names, etc), played from Katie's point of view (complete with Match 3 combat). It could have been fun, but in the end I shelved it as being too much work.
Instead I'm integrating a number of smaller sequences played from Katie's point of view; dealing with the aftermath of the bank-job and touching on her relationship with MC, the clan and the other characters in the game.

It's a lot of fun writing Katie; she's far more introspective, and darker, than MC. Hopefully she comes across as a unique voice of her own, and you guys will enjoy the times she steals the show.
I've got another 3 or 4 sequences from Katie's point of view, before I return to the Dresden assault, and finally the Corpus Christi event.