So I've been working a bit. Initially I was looking for a script of some sort, or an executable I could decompile with the tools at my disposal. But, getting to the point. I've written a python script which will extract all the files from GMP archives, which contain map and model data. I can also view every map from every scene and battle in the game (including textures, lighting, shading), just trying to figure out the best way to export them into a more human-friendly (read: walkthrough-friendly) form.
IPB Image

GMP Tool

For reference, here's the spec I wrote up for the GMP file format:

GMP files are model archives that typically hold one or more GMO (3D model files with embedded GIM texture files), GIM, attr, and other file types. Gungnir appears to use them as self-contained scene descriptors, sans animation controls and whatnot (likely contained in the .bin files accompanying seemingly every GMO file).
    Header (0x10 bytes)
    File Descriptors (0x20 * number_of_files bytes)

00-03: Number of files
04-07: Where descriptors start
08-0B: 0
0C-0F: 0

00-13: Name
14-17: File run length
18-1B: File start
1C-1F: File function (or, perhaps, even, a layer index?)
This is what I've seen:
    0: Terrain (or something of the like)
    1: Shadows
    2: Fluids? (The only GMO labeled with this that I've seen was a lake in the map)
    3: Unknown (I've been unable to open any GMO files labelled thusly)
    4: Object (like boxes and furniture, typically destructible objects)
    5: .lightMesh
    6: .floorMesh
    8: Clouds? (Only ones I've seen were clouds)

From my explorations, typically 0, 2 and 4 are the ones of most interest to us, as they give us the textures, shape of map, objects and hazards, but I'm still poking around. Also not sure exactly how I'm going to go about this. I may need to learn some 3D programming to actually make these things useful.

Would people use them to make a guide? I'd love to see that.
Otherwise I might not bother. :/