The challenge is simple - replace Arabic as the primary language of communication with French in the countries of Morocco, Algeria, and Tunisia.
That's going to be insanely hard. Arabic played a huge role into pre-colonial societies of North and Sahelian Africa, as the religious/judiciary/political/societal language of most of its societies.
The structures in places, contrary to most of Subsaharian Africa (and even there, French remains essentially a vernacular language, not a primary language of communication), remained largely in place (and not only in the protectorates) as another way to separate the native population from french administrations or population. (cf. different statutes).
You'd need to break North African societies so hard that they'll lost their own cultural features, there. Safe a massively traumatic and bloody event, which would be both costly and going against interests of French colonisation...
and no ethnic cleansing on a scale greater than what happened OTL.
Wait, what? French colonisation was without a doubt an oppressive system, including war crimes (Rif War,Setif, Alegria War) but ethnic cleansing?