I'm actually working on another game right now where the conceit is that you can have your friends loop with you... and yes, an exponential level of tracking!
That's wonderful to hear! Not just that I'll get to play another beautiful game with similar mechanics, but that you've grown as a game-smith, emboldened to take on the more ambitious!
Hopefully there's room enough for a few more cozy side scenarios. Being a repeat witness to "The end of days" might be a bit taxing on the 'ol sanity of the characters, methinks :)
But don't let feature creep in too bad, I'll want to play it before Half Life 3! ;)