Already exists. Get it here. And stop asking questions about GBAD1 hacking here, Kippykip already said that he doesn't know how to make hack for GBA Doom 1.
LEAFS lump only exist in Playstation Doom and Doom 64 for Nintendo 64. GBA Doom doesn't use LEAFS as far as I know.
Any ideas who can help with this? As far as I know Randy is not interested in making vise-versa converter