Give citizenship and rights to native locals, especially Berbers and promote a synchranist Franco-Berber identity in the locals in preparation for eventual full frenchification. Highest priority is to reduce influence of Islamic religion/Arabic language, which not only go hand in hand, but are opposed to western values. On the other hand, Berber culture should be much more easily reconciled with Christian Europe, as they too were once Christian and part of the greater Mediterranean European sphere.
Basically, the French might find it difficult to get rid of their demographic disadvantage in terms of "white french" presence, but if non-arabized Berbers are deemed "white enough" it could tip the scales in favor of continued French dominance and eventual full integration.
This would have to start as soon as the French show up in the 1870's and the shift should be in full swing before the 1940's/1950's to prevent the popular success of the arab nationalist movements that sprang up by the 60's.