I currently have the character portrait GUI app and a working script compiler that is a command line tool and not exactly user friendly.
I plan on staying away from maps for now. There are plenty of existing maps to repurpose.
I also have some handy resources such as a Sappy.xml with tags for the game, a list of units in ROM order and a list of Pilots in ROM order.
A thorough liking for the series sparked the idea of hacking the games.
Resources used and process:
Monkey Moore for the text table, truly excellent program for finding character tables.
Textboxes were found by just looking for a pointer to the text once I could see where said text was. Then I hit a snag, there was nothing pointing to the textboxes. Through that route I could not get a hold of what makes the stages tick.
Enter VBA SDL-H. The next thing I did was plow through traces looking for something useful using the address for the textbox. Eventually I came across something that looked a whole lot like a script parser. I fired up VBA-SDL-H set myself a breakpoint and observed. Rregister 1 gave me the offset of the script being read. Now I'm in the process of figuring out what all the functions in the scripting language do.
Through this I also found a "master table" containing a bunch of pointers to the different things that make up a stage, for each stage.
The portrait graphics were found using Tile Molester, they're not compressed.
All other graphics turn out to be compressed and readable through UNlzGBA.
On a different note. I recently headed back into ROM hacking. Not in Pokémon games though, but in Super Robot Wars Original Generation 2 for GBA. Mostly to see what I could figure out, in the meanwhile however I've almost figured out enough to start making an actual hack!
Stuff I figured out in order of discovery:
-Character portraits + Visual Basic program for inserting and viewing them
-How textboxes are defined
-How unit spawning is defined
-Currently, after staring at a debugger all day: delving into the scripting system