I don't know a way to "edit" a savegame to make changes to the regions (countries liberated by france joining them in a full nato-WP-style alliance)
but i guess a small workaround should do it:
1. export your savegame as a new cache (..its just a copy of your .sav file to the \cache folder)
2. make a scenario that uses this cache
(i would take the same scenario file you used to start that game, make a copy of it ,
rename to something like WW1Aftermath to easily identify, edit that scenario file to use your exported cache)
3. then for liberating those countries you could use events:
see vahadars very detailed tutorial viewtopic.php?f=79&t=26056
4. add those in a custom .csv that is also mentioned in your scenario file.
but for balance reasons i would rather leave France as a big blob.
Don't forget to post it!
my mods viewtopic.php?f=79&t=25932
(even techs and units for everyone - AI will own you too)viewtopic.php?f=87&t=26151