Step 1: Byte-swap

Using the byteswap_2.py script from Keitai Archive, create a byteswapped version of the file

python byteswap_2.py D900i_PF48F4400L0ZDQ0-f1.BIN

Step 2: Assemble

Using assemble_d900i.py script from various-keitai-assemble, process the byteswapped output

python assemble_d900i D900i_PF48F4400L0ZDQ0-f1.BIN_2swapped.bin