This is a valid point of view. However, in the current french constitution, as it, the elected president has the final authority over the army, which even without the majority at the parliament makes the president able to manage foreign policy. (Sure the parliament can not vote the budget which would technically limit this power).
If Macrons wants to send troops to Ukraine next year, Le Pen, won't have many way to stop him. Well, the parliament can not votes the budget which would strongly limit the ability of the "troops" to work effectively, but that's it. In the previous case of cohabiation, it wasn't a big proble, conservative and socialists are reasonable person who can work together well enough to find arrangement on foreign policy. Think can be more complex with neo-liberals like Macron and far-righter like Le pen