In Joseph's North Africa strategy, he never planned on using the French Army to force his way through from start to finish.
Not only would that approach heavily deplete the troops and cost a significant amount, it would also easily provoke fierce resistance from local forces in North Africa.
Countless examples from later generations show that defeating the enemy's main force is often not the difficult part; the real headache starts when cleaning up scattered local militias. For instance, a future world superpower managed to defeat Atta in just over ten days, but then spent 2 trillion US dollars over more than a decade fighting guerrilla groups, and still lost in the end.
Therefore, the best method was still to mobilize the local forces in North Africa to work for oneself, and have a small contingent of elite French forces act as a counterbalance to influence the final victory or defeat.