the file you wanna reimport gotta be the same width, height, format, same amount of mipmaps and overall filesize and data structure. how you edit or copypaste this isyour problem, as long as the file is a correct and valid pvr file with this particular name, yes.
i dunno about any other file formats that allows the etc and astc compression as a data block format. there's a modified specification to output etc and astc into the dds container, but i think this specification is not official and i don't care to find an image editor that implemented this inofficial format support. hence why the pvr (the actual gpu manufacturer) specification as the safe choice.
and... no... i'm not into fifa modding (or soccer in general).