Re: My first AAR : any suggestions or advices are welcome!
Welcome to you as a new AAR writer! I look forward to discovering your character. Using historical elements, when they help your story, sounds like a good idea.
You asked for things to avoid or which would be beneficial to address. I suggest thinking about what motivates your character and how his expectations, values, hopes and preferences were formed. What did the previous generation (such as his parents) do which annoyed him, or which he swore he wouldn't do when he got older? What does he look for in a good friend? If he's a high-status character, how does he treat low-status people in his society? What does his think is the greatest danger to France? What lessons in life does he need to learn?
If you want to keep your reports immersive and polished, then I suggest keeping them relatively brief and posting no more than one update a week, even if you have other updates ready. With shorter updates, you need to spend less time writing which gives you more time for editing. If you post more than one update a week, then readers might struggle to keep up - it would be a shame to lose readers.
I suggest reading other AARs and creative writing, not to copy what they do, but to help you see what styles you like. This also shows how much freedom you have. For example: some AARs have a lot of screenshots, others use few or none. Some focus on in-game events, others have in-game events happening in the background (or don't rely on a campaign at all, and just use the game as a setting.)
I suggest commenting on other AARs and creative writing, because this will introduce you to the community of writers here and it might encourage other writers to comment on your AAR (especially if you include a link to it in your signature).
Critic's Quill articles might help, such as Dodging Bullets: Overcoming problems when writing AARs, Writing a First AAR: Ten things you can do and My Ten Rules for Writing an AAR. There's a full list of Critic's Quill articles, with links, in the Log Book of Juvenal (a sticky thread here in the Writers' Lounge).