A C/C++ developer should have no issue building his own core after replacing the macro code at https://github.com/libretro/FBNeo/blob/868dee240104ed2ba3b74ec0bc3c9f467fb284f8/src/burner/libretro/retro_input.cpp#L200-L259 and https://github.com/libretro/FBNeo/blob/868dee240104ed2ba3b74ec0bc3c9f467fb284f8/src/burner/libretro/retro_input.cpp#L1812-L1821