there is only a highpoly model of her in the wedding dress as far as I'm aware of.
They are not usable with battle/generic animations.

FFX-2 models in FFX? not possible. unless you wanna see something like this because the bones in the animations don't match:
https://www.youtube.com/watch?v=Mz2FJ6gDq3U

You can't just take the model files and replace them, you have to completely rerig them or change the bone id table somehow.
Without the matching PhyreSDK version impossible to do.

look here: http://forum.xentax.com/viewtopic.php?f=10&t=14340&sid=5562ce2244eaedb29082cd77d04baa13
and here: http://forums.qhimm.com/index.php?topic=16943.msg240957#msg240957

It would be easy to swap out the models but all the animations Tidus has probably wouldn't work on the Jecht model or Yuna's on Braskas because the bones don't match.
I tried that on the PS2 version and the result came out with something like this: https://www.youtube.com/watch?v=Mz2FJ6gDq3U

It would be also a little weird to have Braska sound like a girl unless someone wants to do a lot of voice acting.

there is a VBF packer now, should be possible now to export textures using the Phyre SDK, replace them and repack the VBF.
textures are gonna stay permanent without the need of UNX.

like you see on the screenshot above, its not so easy to just cut them out and put them on the remaster texture.
The alignment of the textures is completely different.
You will have to do a lot of more work than just copy pasting.

how could they forget her teeth?

ok don't bother about the PS2 faces, it takes A LOT more work to do than just a simple replace.
here is why: http://prntscr.com/b4yp1c
they completely overhauled the models and the UV map is completely different..
highpoly models have textures up to 2048x2048 pixels btw which is a huge improvement to the 512x256 ones from the PS2 version

If an artist can just work on the makeup, go right ahead.
I just don't wanna do something as the bad artist I am and then people will just complain about it in the end :p

All I need is Noesis or Yaz0r's ffx2obj tool, UNX and photoshop :p
I will release it as texture replacement for UNX.

I'm not that great of an artist so I will just try to use the faces from the PS2 textures.

Noesis is a great tool to work with the PS2 models btw:
http://richwhitehouse.com/index.php?content=inc_projects.php#prjmp91

For everyone who doesn't know what UNX is:
https://steamhost.cn/steamcommunity_com/app/359870/discussions/0/364041517007524857/

Kind of a musthave tool now for FFX mods.

that could be done with a simple event ID change