Now that I've played through this for the third and fourth time (the first two runs were around 2019/2020), I'd like to share a few thoughts on it.
BtA is one of the best mods, definitely among my personal top 5. The hard work put into this and the extremely high production value are visible from the beginning, even from before starting the first mission (newsroom, system map). I totally like how you exploit FSO tools to give the player new functions and gadgets, extending the gameplay beyond the original games, while staying faithful to the classic Freespace experience. This is still Freespace at its best, enhanced with new stuff provided by this community. I wish I had the fredding skills shown by the BtA team!
Regarding world-building, I cannot say what hasn't been said before. Outstanding work here! In this regard, BtA is probably the best campaign out there. No other mod I know does such a good job at giving the player the feeling of actually being part of a bigger universe, inhabitated with people, institutions, corporations, factions, you name it, which and who - and this is the important part - do have a backstory. Even with things that do appear only once during the campaign, you leave them with the feeling that there is more that could be told. Hastings depot or Detiula station are not just some items put into the mission by a fredder. They are things that someone in this universe built once and that have a story to tell. It has been said before: BtA puts meat on the bones and shows that there is a world in Freespace outside the military.
The soundtrack: I heard what you did there.
Total Annihilation,
Game of Thrones and
Dune (the Lynch version) are pieces I recognized. It's nothing memorable by itself (for me at least) but this is exactly its strength as it nicely blends in with the somber, tuned-down mood of the story. The same is true for the background images. The content, the look and the sound of this mod organically come together - nice!
The story itself is solid and builds up stepwise. I like that you often deal with everyday stuff like patroling a station or protecting civilians. There are plenty of hints for larger things that will happen in sequels. To be honest, I'm a bit skeptical of some of them because atm they look like this could become another universal armageddon story. I hope it doesn't. But let's see what future releases bring.
The only main building block which is too underdeveloped in my opinion are the characters. There almost are none. Alpha wing is consistently voice-acted by the same actors, so they are the same people in every mission. Then why not give them a name and some background? This and the player character being a mute are strange anomalies in such a lively universe.
The Battle Snails... my heart is not in this. In my latest run I looked them up in Fred to find them all, but... meh, I don't know. Well, it's just a little gimmick which can be skipped. I appreciate the effort, though.
Another very minor thing: I feel like the AI could be a little more collision-avoiding.
A few thoughts on some individual missions:
The Will to ActA lot of people seemed to have struggled with this mission. To me it didn't really stand out in terms of difficulty, though I usually need more than one go to beat it. I never had any trouble evading Cancer wing. In my recent runs, though, I was totally unable to destroy the HoL base's comm system which I swear was doable before. No matter how close I place my charges, it always stays functional. The directive to mine the fighterbay shows fulfilled after two charges already. And it always frustrates me that Sermakh just sits there after he has gained some distance from the base. He could be a little more evaside imo. Despite these issues this is a cool mission.
Acts of VolitionThe helplessness comes along great! It's so frustrating and painful to see all those poor civvy ships go boom.
Bringing Down the GavelAs with many other people, this was one of my favourites. Innovative mission design combined with some good old simple "blast outta the space whatever's in yer way".
To Steal a March OnThe only mission I really don't like. I know it's
supposed to be frustrating but this one's too good at it.

I really think you should tone it down a little bit by putting fewer enemy fighters in here. It's just too much. Plus: why do I have to fly a bloody Herc? The Herc sucks!

Plus, the "skip intro" function does not work.
The Texas SevenCool mission. One of my favourites. I started it at 12% hull integrity during my last run and made it. Wohoo!
The Armageddon ClockA solid dive into the intelligence world. Thumbs up! The text is placed a little to deep, though, and sometimes overlaps with the radar HUD.
How the West Was LostArgh! On the one hand I love it because it's one of these great pieces that really drive world-building and immersion. On the other hand these magnetic grappler dudes are *****ES!!!

And the convoy escort part is really, really tough! Also suffers from a few glitches: Hexamere suddenly speeds up and outruns the rest of the convoy. Alhambra was still in-system when I was given the RTB order and then I got my ass spanked by Lt. Maria because I did bad-bad during the mission. I didn't really get whether I lost ships to enemy fire or this is a bug. Just wanted to mention it. The first jump sequency is faulty.
Rebels & RevolutionariesWhy, why, WHY?!?!?! Do I have to fly this crappy Herc?! The Herc sucks!! Why do you do this to me?!

And then this Command dude even mocks me telling me to evade the escorts. Move your ass out here and do try yourself in this damn tin can. To quote Lt. Mackie: Grrrrrrrrrrrr!!
Groundhod DayCool! Although targeting is somewhat tedious this is a great mission which shows what can be done when a skilled Fredder is at work. Thumbs up for this one!
Two minor things: The Snail does nothing. Please use another key combination to fire the turrets. I constantly hit Alt-1 instead of Alt-Shift-1 and end up in that other display.
Going Out With a BangThis one's a *****!

A tough nut to crack for the finale. Even though I curse a lot whenever I play it, it's a great ending. Just this morning it came to my mind that hiding in the Cardinal's fighterbay might either be a very good or a very stupid idea. Gotta try it out anytime soon.
Oh, and why is Khonsu already called the second when he is not emperor yet?