Starting with some rerips (map layers + full maps). I was able to circumvent the map teleports by using codes from GuardMaster, which locks the player coordinates somewhere on the map.
7e1181XX (x coordinates) / 7e1183XX (y coordinates) didn't have fix values, but I played around and found that 60 for both was a good one. I was able to walk around the edges, make screenshots and put everything together.
Luckily, the palettes for the map tiles didn't have any rgb (0/0/0) black in it, therefore nothing clashed with the bg colour (at least for the Jungle, Riyadh partially needed the Tilemap Viewer to retain the black in its huts).
Unfortunately, I wasn't able to use Tilemap Viewer for the entire map, since I needed a certain position of my character to get seamless map portions and everything beyond the edges was very glitchy and going too out far would also affect the map itself.

Those debugging sprite and tile viewers are just too good. I wish other emulators had them.

You're welcome. But one day I want to come back to this game and rip the remaining party members and do layered rerips of the maps.
So far, everything here was ripped with either bsnes-rawpalettes (maps) or vSNES (rest), which is fine since both of them use true colours.
For the future, I only want to use bsnes-rawpalettes, since it's really easy to handle and can do everything vSNES can.

Thank you for this delightful work

Lots of research, I would say ;-)
Btw, the exterior maps use teleport spots in all directions, meaning one step too far and you will leave the map. I captured all of them one tile before the teleport activates and I assume they're larger than what I submitted here.

How do you keep finding beautiful games I've never heard of? O_O