Beethoven composed a hymne to Napoleon which He destroyed after he crownwd himself emperor.
No, that would be his Symphony no. 3. He
dedicated it to "Citizen Buonaparte", but then he heard Napoléon had crowned himself emperor, and scratched the dedication out of the title page so hard that he tore the page. Ludwig rededicated it "to the memory of a great man (Eroica)"
Composers in Napoléonic France:
Étienne Nicolas Méhul (had already done some extensive work for the Republic, was sort of in favour under the empire)
Jean Xaviere Lefevre (professor at the Paris conservatoire)
Rodolphe Kreutzer
Nicolas de Layrac
Pierre Vachon
Jan Ladislav Dussek (was the "Kapellmeister" of Prince Talleyrand's household, ICR the name of the guy who succeeded him. I read it in the last week. But at the moment my head is so full of frigging Chopin and Dvorak for a concert that I can't remember much else).
Jean Baptiste LeSueur
Luigi Cherubini
Gaspare Spontini
Napoléon liked Paisiello (who composed the mass and the Te Deum for Napoléon's coronation), although the French loathed the man. So much so that Napoléon was obliged to send Paisiello on his way (Paisiello had staged an opera in Paris, that was heckled so badly by the audience - which included Méhul, Grétry and some others whose names I can't remember - that although the First Consul liked it, Boney was obliged to send Paisiello on his way when Paisiello informed the Consul that he could not earn a loaf of bread outside the palace).
I can't see Napoléon letting a non-Frenchie write the French anthem. So scrap Dussek, Spontini and Paisiello from the list. (Kreutzer, despite his surname, was French - not to be confused with
Conradin Kreutzer who was German - and Cherubini (whom Boney personally disliked, despite his patriotism) was a naturalized French citizen since the 1790s already). Méhul has already had some success at the Paris opera, Lefevre wrote the clarinet exams that were still being used at the Conservatoire until the 1960s or 1970s IIRC. Vachon died in 1803, so unless the anthem is set to one of his tunes, it's unlikely. And De Layrac is former aristocracy, so I
don't see him writing an anthem (or even Napoléon being entirely comfortable with him).
Hence I second the opinion above that Boney will go with an existing anthem. My personal preference is the Chant du Depart.