Kaiton,
Great to chat to someone who is into this stuff. By the way, some guys are trying to get a going for general adventure game development.
I'm not sure I explained the track thing. The concept is that you don't have to put in pathfinding code (which I've heard can be a bit CPU intensive, depending on how it's done).
I use the terminology "stage" (as in the theatre) for a room or screen that the character walks around in. When we create each stage, we specify various co-ordinates which the player will have to walk to, then link these up with tracks or paths of your own choosing, so the character always walks where he/she should (like they're on a train track). Of course, this means you can't make the character just walk where you click on the ground, but I've always felt that's a redundant feature. Another advantage is you don't even need to put in no-go zones.
The disadvantage of the "tracks" system is that you have to define every place that can be walked. If you want to get NPCs in there walking around, and dynamic locations for conversations, it falls on its face. I haven't committed to it yet. Still weighing it up.
You're absolutely right about splitting up the game for the PPC. That's my goal as well. I want to do it in little chapters.
About defining the adventure, this is a BIG issue that I'm trying to decide on. Your references to Indiana gives me the impression that your concept has been inspired by IndyJava. That scripting system appealed to me as well, but there are many others. I don't know enough about any of them. At the moment, I'm still coding the classes to make it all go, but someday I'll have to get on to the interpreter.
I'm interested in this parallax scrolling too. It suggests that some of your stages are wider than screen-width. I was thinking of making some stages connected with a quick scroll when you reach one side, so you get the impression you're still in the same "room".
Finally, have you thought about the virtual theatre idea that Revolution software used in a couple of their titles (like Beneath a Steel Sky). The idea is that even when NPCs aren't on the visible stage, they go about their business on all the invisible stages in real-time.
Shapeshifter: Speech wouldn't make the interpreter much bigger, but the main problem is usually the lack of good voice actors. Very few adventures I've played have good enough voice acting. I personally prefer text.
Trevize