I've already locked in the characters as is, mainly to avoid a flaw.
The endless character selection flaw that most interactive stories on the site suffer.
If this interactive story doesn't work out I may try and redo it and allow everyone a little more freedom in the story and character creation, allowing you to add your own characters as you see fit.
I hope that is okay? Your characters can make cameo appearances if you like, but they cannot replace any of my characters that I have listed.