As for overall French plans in the Saar, there isn't much. I've found very little in the way of English language publications, perhaps nothing more than one or two sentences or a paragraph at most. Ernest R. May (Strange Victory) has a little bit to say about it, but not much.

I'm sure there is something in French, though I do not have it. The only sources regarding Saar operations I have, is what I've listed earlier on this thread:

Alain Legrand's-Alain leBerre's "La Bretagne a l'epreuve - Sarre,Flandres, Dunkerque" (devotes a whole 9-10 pages on this, mostly derived from individual accounts)

"8 Septembre, 1939 - Cette Nuit Nous entrons en Allemagne" by Bertrand Le Barillec (I learned that apparently Barillec has - or had - in his posession many personal papers of General Mast and draws much of his information concerning Saar op. planning - or lack thereof- from them.)

another book I have is "Les Grandes Unites Francais" S.H.A (1967) -has some mention of overall objectives for the entire 21e I.D.

They all more or less say the same things: to capture a series of small towns and villages running parallel to the Seigfreid Line, dig in and wait for the artillery (probably elements of the 35e and 255e artillery -attached to 21e I.D.) to be drawn up. Then they were to destroy the Seigfreid Line, after which the troops would move up and occupy it, ostensibly to deny Germany her western defenses. Beyond that, there is nothing I can find, so your guess is as good as mine.

Frankly, I don't think there were any plans beyond that. My guess is they wouldn't have even managed to do that much. Notes I've taken from a book entitled "La Defaite de la France" by Henri Michel, mentions how the attached artillery observers couldn't tell where shells were landing since many failed to explode (old WW 1 inventory, perhaps even older).

Other than that, I have nothing else in my personal library solely devoted to Saar operations, though I wish I did. On my next trip to France, I should make a point to find out more.