for the armor you want to change, go to the coinciding sections' "equip_template" line and change the text after the equal sign to "geralt_keadwen_ghost"
edit: i actually said something wrong back there, it's been awhile since i modded this game, but you can also replace geralt's armor with letho's armor, as in the picture.
it's called richon_body
but as you can see, it's quite ugly.
i also managed to give geralt the beaver hat. i did it by editing the file "def_item_trophy" and changing the model name of one of the trophies into "q208_zyvik_fur_hat", then you can equip that trophy and wear the hat.
insert edited file inside their original directory folder into the cookedpc folder.