I see you're the kind who, when confronted with a genie, always asks for more wishes. I respect that, and so I will do my best to tackle all of these--and without copping out by saying "because it looks cool" or "because it's more fun." Because there is always a lore reason, even if I have to bend space and time a bit to fit one in. :)
How closely does the in-game usage of the weapons reflect their in-universe fighting styles? Does the sword rework reflect a canonical change in sword usage?
I think Trainer Rosk, Kat, and your other mentor figures are always studying and learning new techniquest themselves, and this shows in how weapon use can change and evolve. But tbh it's not a major part of the story right now--but it's an intriguing idea to pursue!
There's a statue of the first slayer in the Ramsgate plaza. What behemoth's head is he standing on?
It's a "best guess" impression of a legendary Behemoth the First Slayer faced, but which is described in different ways in many cultures. In a way, it sort of represents an Ur-Behemoth. Most cultures call it some variation of "Leviathan."
One of Strega's voicelines mentions that she hasn't worked "this hard" in this life or any past life. Does she really remember living past lives? If so, how can she have those memories?
I've searched and searched and can't find the line in question. But if she did imply she remembered "past lives" that was a figure of speech.
When Skraev got remodeled, did the Skraev population in-universe canonically change as well?
Sure looks like it! In lore terms, this is a realignment event for the species--certain traits becoming rapidly beneficial and (thanks to the weirdness of living aether) influencing the physical forms of individuals in precisely the way actual evolution doesn't work.
How much do the various weapons actually weigh?
Light enough to carry, heavy enough to do damage.
Give me a specific weapon and I can come up with a number :)
Why are the weapons shaped the way they are? Something like the Quillshot axe should be absolutely horrendous at cutting much of anything, but it seems to work fine in-game. Would behemoth weapons be useful in regular human warfare?
In lore terms, the power gained from using Behemoth parts combined with Slayer weapon training (and study of Behemoth weaknesses) means weapons needn't necessarily look like a traditional example of their type. The terrawoven weapons of the Farslayers, for example, look like carved sticks, but thanks to the way they're made they're as functional and sturdy and anything made from metal or stone.
The Quillshot sword, for example, is more of a spiked club in appearance, for example. But the techniques used to forge the weapon and the way aether is worked into its structure affords it a cutting edge,
How do different behemoth reagents change the perks and UEs of their respective gear?
I think I'd need some examples on this one.
We find blueprints for exotics (except TS, which are Lady Luck's own design) in patrols. Does that mean someone left the schematics for these items lying around? If so, who made them, and why?
Different exotics were designed by different smiths for different purposes (each one unique). Conceptually when you recover them in the wild you are finding either copies of the original schematics that were lost for whatever reason over the years (remember all those Ositan harpoons on islands? Most of these were probably fired decades if not centuries ago--people have been sailing these islands for a long time).
Moyra mentions seeing something other than behemoths tearing into Ramsgate, as well as each other. Is there any chance you can tell us more about these guys? Are these the "Aetherbeasts" taken off the roadmap so long ago?
I need more context on which line you mean here. It could have been environmental danger (if she's talking about the Umbral Deeps, falling umbral boulders tore into the city quite a bit), packs of dangerous fauna that have since seen their numbers reduced, even warships, depending on the point in history.
The journal confirms that humans made behemoths. When, why, and how did they do this? And how do modern humans know about the behemoths' origins?
I'm not going to delve too deeply into this one right now because this question in particular is something I want to work on answering in-game. But the last one I can answer--the Orrery has preserved not just all the knowledge acquired since the Upheaval that they could get, as well as a surprisingly large collection of pre-Upheaval documents. They jealously guard these and only the highest-ranking members of that institution can gain regular access to this knowledge.
How long ago did Janek and Lady Luck bone? Because we all know they boned. Each other, to be exact. Also, what base did they get to?
Sorry, getting a lot of static on the line. Could you repeat that, but like, classier?
We've heard a lot about the "aetheric spectrum." What exactly does it look like? Is it something like the electromagnetic or visible light spectra? How well-understood is it? If blaze and radiant aether can "resonate" at the same frequency, what exactly does that mean?
It is very much something like the electromagnetic and light spectra (and high-five for the proper plural, my friend). But it's not exactly light, not exactly magnetism, it's a thing tht honestly I will someday go into in MUCH greater detail, but think of aether as something that can exist in every form of matter known--but it's ultimately a source of energy, even when it's solid in the form of archonite.
The Orrery and specifically aethersmiths like Arkan probably understand the spectrum the best, as they don't just work with these materials but study them and aether itself extensively outside of their practical uses. (I.e., they will study aether's effects on various elements, the half-life of aetheric isotopes, that sort of thing, not just "terra opposes shock and vice versa.")
How big can a behemoth get? How much do behemoths weigh? What substances are their bodies made of?
No one is entirely sure how big Behemoths can get--some Orrery scholars believe there are truly massive Behemoths lurking beneath the Sky Below, deep within the heart of the Maelstrom, or even encased within some giant, unsettled rogue island that's drifting through the skies waiting to crack open and unleash hell.
As a basic rule of thumb, though, they tend to reach an average mean size that is around what you see in the game, since their access to resources (and the amount they can eat) doesn't really change, at least not in the parts of teh isles that we're hunting. But if a Behemoth was left to its own devices, had a steady source of aether, no Slayers to threaten it or other Behemoths to compete with, and plenty of time, it could theoretically start nearing kaiju size.