Interesting notion, but apart from anything else, I'd still have create some entry-exit points for the scene script when called from the gallery (or duplicate a ton of script and keep that in sync manually for changes, which is not a good option), and that means I have a ton of variables to seed for the dialog, and I'd have to capture those from some 'canon' playthrough, and if I figure out how to do a capture and seed mechanism for my playthrough, then we're already most of the way to capturing and seeding variables from your playthrough.
It's an interesting problem to tackle to be sure, but for now, saves will have to suffice.