Alright, so. It turns out the item stats are in one of the files in media.fpb, in the old NBL format.
This is Sword:
0000 0014 2BC0 1110 00 4C 8700 150020 FE 0150 0A 78 5200 8014 00 05 00 00 00 00 00 05
I haven't figured everything out on it yet, but... here's a rough skeleton (if it's not labeled, I don't know, and can't even guarantee the data size):
00: Unknown (PSU had a couple things here, not sure which ones are being used here--I notice the )
00: Model number
00: Visual effect (e.g Crimson's flames)
14:
2BC0: top 2 bits set (mystery) + 0x2B: probably minimum ATP for variance (43; 43-71 ATP seems reasonable?)
1110: Lower 12 bits are (weapon ATP - 3) / 4; 0x11 * 4 = 68 + 3 = 71 ATP. Next three bits (the "1" in 10) are SE level (runs 1-5, although technically you can set it up to 7), not sure what the top bit is.
004C8700: First 11 bits unknown. Next 12 bits extend ATA bonus. Next 9 bits unknown.
150020: First 13 bits are ATA (unremarkable). Next 5 bits are SE number. Not sure what remaining 6 bits are.
FE: This is consistent, whatever it is.
01: Level requirement
50: Level requirement (extended)
0A: This one's related to PP costs/PA damage multipliers (it may be an index rather than a multiplier; Yohmei has 9, Tenora has 0xB, which matches both percentages, but kubaras can have 1, 8, C, various other values)
78: Second extension level requirement (120).
52
00: Set? Agito Repca has 31,
8014:
00 05 00 00 00 00 00 05: Base stat bonuses, 1 byte each (Sword gives +5 DFP and +5 MST; presumably this is ATP/DFP/ATA/EVP/LCK/STA/TP/MST)
This is very different from the PSU format.
On the other hand, though, the unit format stayed exactly the same.
Including attack/tech speed bonuses.
I wonder if they work?
EDIT: Alright, so. On head units, all 3 modifiers (tech speed, tech range, tech PP cost) will still display when assigned to a unit. On arm units, "melee speed" has been removed, but the other 6 ("Auto Damage", firearm range/speed/PP cost, and striking range/PP cost) still display. Auto Damage (this was a damage over time), striking PP cost, and tech range/PP cost/cast speed don't seem to work any more; I'd assume the remaining other ones do not, either. I kinda expected this, but on some level, I'm still a bit disappointed.
EDIT AGAIN: Looks like the same data is at the end of the 0_ITMi14064013.unr file (forgot which weapon this was):
01 03 2A12 9600 32B0 90B1 24 00 462019 FD 0150 09 08 9301 1A 82 00 00 00 00 00 00 00 1E
Presumably the model number works differently seeing how the weapon carries its own with it. That said, in theory, if I didn't read it wrong...
0x96 min ATP, 0x32 * 4 + 3 = 203 ATP (in theory--I feel like the control data for this _must_ be somewhere), 0xB & 7 = level 3 SE, 0x46 ATA, SE 9(?--this'd be Confuse), level 1 requirement, +0x1E (=30) MST.
Looks like I was... surprisingly close! According to the wiki, it should be
(unknown min ATP--it's never displayed in game), 200 ATP, level 3 SE, 70 (=0x46) ATA, confusion, +30 MST.
[゜Д゜]<インフィニッティー♪
EDIT again: The "3" on Sword comes from the top 2 bits of the minimum ATP. On Sword, that's 2BC0, so it's 3. Yes, this means the entire thing is probably ONE GIGANTIC BITFIELD, the things falling on byte boundaries (except at the end) are just a coincidence.
EDIT again (again): Filled in a few more values. Looks like the actual extend ATP bonus and SE are stored in one of the other files:
00000101 45020000 96000000 21000000
00000101: Sword's item ID (01010000) in the wrong endian.
45020000: First extension ATP bonus.
96000000: Second extension ATP bonus.
21000000: Bitmask for valid added SEs.