For anyone that's interested in such things ... here are some stats (from my current knowledge, I may still be missing something).
The game contains 118 major data files, which contain 5619 compressed data chunks.
Of the 5619, it looks like 646 contain program code, and 546 are part of the in-game data-streaming system.
Of the 646 chunks that contain program code, it looks like 292 actually contain Falcom's scripting language (all text strings are stored within "script" data) .
From a programming POV ... the title itself boots a small "permanent" bit of code/data, which then loads "overlay-sections" that contain more "semi-permanent" code/data.
The "in-game" section appears to handle all of "normal" gameplay, including the cutscenes.
The "in-game" section switches between different 128KB META_BLOCK data files as you move around the game.
Each META_BLOCK contains lots of compressed 8KB-maximum DATA_CHUNKS (the largest one contains 181) which then get copied to VRAM or executed as you move around a small area of the game.
Falcom's scripting language is a full-on bytecode interpreted language with variables, conditional-jumps, jumps, calls, calls-to-assembly-code, as well as text itself.
From what I can see ... the script code was written in text and processed with a macro-assembler rather than being generated by some kind of level-editor.
So there you are ... that's how Falcom put together their first 2 CD-based console RPGs (and "yes", Xanadu I is using an almost identical engine design).
At this point, the script-extraction is basically done, and it's just being massaged so that it'll be easier to re-insert after translation.