Yeah, I'm edging myself back into the game.
I'm fairly certain you knew this already, but you can reskin PSP models in pretty much the same way as PS2 models or any other models out there. The only real difficulty will lie in re-swizzling the textures afterwards.
Case in point:
1. Take one texture from deadpool_1404.fb (PSP), save into format that is easily
unswizzlable (direct hex rip -> 32x512x4bit DDS). Make a swizzle-base texture (a simple guide - two, actually,
one made of a gazillion 8x32 blocks; and one made of two gazillion 8x16 blocks; for 16-colour and 256-colour textures respectively; simply alternating blocks of different colours within a 32x512 and 16x1024 DDSes will suffice).
2. Take one texture from deadpool_1404.fb (PS2), save into format that is easily openable (direct hex rip -> 256x256x8bit, I'm a barbarian, I know).
3.
Recolour result of 2.
4.
Swizzle, swizzle, little star.
5.
Insert into game, bitch about lack of screenshot taking software, photograph game scenes.Take
some tasty
screensnaps.
I can also tell you now that the _c.fb packages are as redundant on the PSP as they are on the PC. I only modified the texture in the general FB, and left the _nc untouched. Lo and behold, the in-menu texture was the original, while in-combat I've had the mod. Yay. Gonna see if I can strip them out of the WAD altogether to save some space, that would be of much help...
EDIT: Oh, right, nearly forgot.
"Noel, why the heck would we wanna modify the PSP textures and swizzle all that shizzle, when we can instead use the l33t PS2 models with their high-polyness and 256-colour textures?!"
"You see, little munchkin, the PSP exclusives, should you wish to retexture them, have no PS2 models; so sooner or later you will HAVE to do this.
That, and the PSP icons and portraits are in a format that requires you mos def use the original files and mod those, because of the size constraints."
It's miraculous what a hangover can do to one's thinking processes.
Next up: custom portrait checking and my learning how to use the FB Builder.
Addendum: Checked. The icons and HUDs of the PS2 use the same size as the PSP. The only difference is that PS2 uses v3 headers and PSP uses v4 headers; and that the PSP is swizzled. Blunt c&p of portraits allows to achieve a removal of the need to swizzle the HUDs at all. Just don't forget to make sure you either c&p the equivalent file from the PS2 version OR that you've changed all the filenames and internal model number references accordingly and have carried over the FB pre-header for the relevant file. No need to rebuild the FB, even.
Next up: the mannequin, customized model and (drumroll please) custom voice checking. I've figured out the sound format ages ago, after all, so I only need to acquaint myself with ZSMEditor.
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A couple more shots of the X-Men Deadpool custom skin (these are actual pixel size, btw):

So my swizzling technnique is working, apparently. Yay me.
Also, this is how the PS2 portraits compare to PSP portraits when running the PSP version of the game:

So, yeah, I'm gonna make that part of my plan - update not only the playables portraits affected by the Official Characters mod, but also all the others as well, to a crisper, decent-er state. Obviously, updating the non-playables portraits will be one heckuva bitch, seeing as they're all FBed far far away from clear easy access. I need me a better HEX editor, apparently.