Translating the extensive story mode and character interactions is more complex due to text-spacing constraints (Japanese characters often take up less space than English sentences).
If you accept the trade-off (functional menus + Japanese story/dialogue), here is how to apply the best available patch. Busou Shinki Battle Masters Mk 2 English Patch
The patched ISO can be played on a PSP with custom firmware (CFW) or via the PPSSPP emulator on PC and mobile devices. Troubleshooting & DLC Busou Shinki Battle Masters Mk 2 English Patch