Now with grpack - that tool doesn't need any GR.TXT file for packing. Fully automated work with directory with files.

Info:
v1 - unpack compressed (prs) files
v2 - unpack uncompressed files

May be if I have interest and enough free time. --- Some real tools. Copy GR.ARC and unpack.exe/repack.exe to the same folder. Run unpack.exe, wait for "Done" message. Press Enter to close window. Now you will see all files from game archive + GR.TXT needed for repack. Mod any file as you ...

For:
1st build - oblivion.bms
all other - oblivion2.bms