Several years ago, I made a 0% growths patch for FE12. Being done by hand, it had several instances of characters with growths that were not 0%, and it obliged the user to decompile the FE12 ROM, patch, and recompile. So here’s a new version of the patch: all characters have -125% personal growths in all stats and will never gain anything when leveling up. I also included a version of the patch that gives 10x money from bullions, if you want a slightly easier time.
Use one of the included patches on a FE12 ROM with the v3.01 version of the English translation patch applied.