Advance wars save game, anyone test it ?

[Flavor]

Here's something I might try if I were you.
From https://ezflash.sosuke.com/viewtopic.php?t=3165#top

1. download gbata
2. run gbata
3. find the tab named "SRAM Patcher" , click on it.
4. towards the top of the program where it says "file name", click on the "..." button to browse for your unpatched rom.
5. under the "Save as" output alter the path to your preferred directory.
6. click patch

Almost your same question with a simple (maybe useless) reply:
https://retropie.org.uk/forum/topic/1734...n-t-save/2

I'm not sure this is related to your issue, but it's interesting:
https://retropie.org.uk/forum/topic/509/...a-emulator

Another interesting search result that's somewhat related to this topic:
"War Room Challenge 2012 - Advance Wars 2
Hack of Advance Wars 2: Black Hole Rising"
http://www.romhacking.net/hacks/909/