I'm going to get this out of the way so this doesn't feel like a list of complaints: AWESOME MOD!!
The ship designs are absolutely beautiful, and I love the idea of a less static threat than the [REDACTED]. Bringing a heavily themed faction into the game is also great.
However, in the current state, I feel some issues really hold the mod back.
I'll start with the minor: I've seen smuggler fleets using Hiver ships, specifically ones transporting ship hulls. I'm not sure if that's intentional behavior, or if those were disabled and taken in combat, but it feels a little weird in terms of lore/balance/immersion. Hiver planets show up in the market data of items, leading to the player being able to pinpoint them at the start of the game. I think this is very much known, and you probably haven't found a workaround, as it's written into the faction lore (love that). My modding experience is very limited, but you might be able to set limits on their markets so that they never have the highest or lowest price for items. All of that is a bit moot though, as you can see their systems on the map. I'm assuming there's a way to hide these, as pather and pirate systems outside the core sector are hidden from the player, and it would go a long way to make the discovery of the hive feel more natural.
Beyond that is the biggest problem: The invasions. I have no problem with the Hive threatening the core sector or being difficult to fight, that's part of their appeal to me, but with the default Nexerelin settings they start a full-scale invasion of the core sector 90 days after game start, which really doesn't seem to fit with their lore. I'm not sure if it's their fleet doctrine, their insane markets giving them more invasion strength, bad luck, or some combination of these, but I have not actually seen them lose an invasion. I've seen these exact planets fend off [REDACTED] attacks in previous playthroughs, which doesn't fit with the strength level you imply/intend. Part of the problem is definitely Nexerelin's AI, as even though every single faction has lost planets to the Hive they are still coalition warring themselves (mount-and-blade-level tactics). As it is, every single planet that can be invaded (no story protection) looks to be doomed with the default NEX/Hive settings. It's very difficult to balance around a variety of play styles and skill levels, but it feels like the player has to speedrun a large fleet and spearhead the defense on every front to prevent the sector from becoming the universe's largest ant infestation. It holds the entire experience back significantly. {EDIT: I've seen your past comment that the Hive shouldn't be something the player can choose when to fight, and I completely agree. However as it is, it feels like a "game ender" event gets plopped down from game start, which doesn't fit with the Hive being a scaling midgame threat that will eventually be a problem, but not for a while.}
I really don't know how to fix this, as I said my modding experience is very limited, but I have a few loose concepts that could help if added. The Hive could have a timer before beginning attacks/expansion to allow the player to get established. The Hive could slowly expand and not attack until its planets reach closer to the core systems. Hive markets could be adjusted to lower the frequency of attacks. The strength/generation of attack fleets could be adjusted to give AI planets a better chance at surviving them. If you can improve the balancing/difficulty curve of the hive I think it could bring this mod close to the quality of the base game.
The only issue I have besides the above is that the borders on the ships have some sort of artifacting that detracts from their incredible visual style. {EDIT2: I can't tell if this is a result of a weird transparency issue, snipping mistakes, image compression, or hard edges in the ship design. It looks like the vanilla ships use some sort of edge shading to help with this. Not sure - I'm not an artist} Keep up the great work, and I hope you find solutions to these problems.
