Unlikely from the perspective of French policy objectives at the time. Surely they had, in theory, the power to do so, but lacked the will, and the diplomacy involved would be... complicated.
Especially as it would be taken by others (such as Russia) as the signal that Ottoman borders are not inviolable anymore, which would in turn raise very high eyebrows in London. And Napoleon III was seeking good relations with Britain.
Paris and London had both acted as de facto guarantors of Ottoman territorial integrity, most recently in the Crimean War, and France in particular had strong ties with the Porte and feared Russian encroachment there (which is precisely why the fought the Crimean War).
Blatant landgrab at the Porte's expense would go against deeply rooted policy objectives and would put France at odds with Britain.
Also, at the moment France had more pressing concerns in Italy.
It is true that Napoleon III was a relatively erratic personality and very ambitious, so perhaps he go for it at a whimsy. But probably some irritated telegrams from Whitehall would stop him if he chose a course leading to annexation.
It is true, however, that the Maronites would be probably be mostly fine with French rule.