Well done!

As far as switching out files in the base game directory goes, there are a few png files that can be switched out, but they seem to affect only the Escape menu. I switched out the Escmenu.png file for the original FF3 NES background, which affected only the Escape buttons and nothing related to the in-game windows.

I don't want to say it's impossible to mod the font or backgrounds, but it likely involves digging through MSD/NCGR/LZ files now when it didn't before. The font used to be the easy part.

I see language files in the "files" subfolder, if someone wants to go through them they might know how possible a language mod would be.

Fortunately, it seems that switching out sound files is still completely doable in the exact same way as before, so changing music and sound effects is very possible. The way tracks loop in this game essentially breaks up one track into multiple ogg files, i.e. a beginning that plays once followed by a looping middle section. Lining up the specific timing of these track splits and perfecting the loop is the most time consuming part for retro music. As far as I can tell, there are 58 soundtracks, 31 of which will need to be split, and 386 sound effects. It will be time-consuming to switch everything out.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2104282388

Something about the UI updates the devs made recently affected this tweak. There are numerous font files in the Final Fantasy III folder, but switching them all out doesn't seem to do much of anything anymore.

I've started working on a retro mod for this game, changing the font and music to the original FF3.

Here's an Imgur album of the font.[imgur.com] It's worth pointing out that the font is this size because to make it bigger would require making the menus bigger, or creating a whole new word wrap system. It's not perfect, especially with the lines that appear occasionally, but I like it.

This is as simple as switching out the arial.ttf file with a ttf of your choice, with the filename changed to arial.ttf.

I've started on this. Definitely possible, but with the way the game splits tracks it's going to be tricky.