I just watched your video on youtube and it seemed that it was a real video (encoded with the mobie? clip coded that is only available by paying money) but at the second look it's looking like I am wrong.
The intro is a mix of 3D rendering and 2D images (you probably found the names in the rom as well) so it's almost sure to say you probably can change it.
My quess is the 3D file at the beginning of the filelist (the ones marked on the pic).
I suggest you go to the personal projects section in this forum and grab the latest version of console tool by Low Lines and try to open those files.
If you find it, you can extract it but not reinsert it.
To reinsert it, you have to try with Tinke (http://gbatemp.net/topic/303529-tinke-072/
) and hope that pleonex implemented already the function to reinsert the textures.
If not, I actually don't find it so bad that it show the japanese name shortly, just correct the position of yours so that it doesn't jump around :p
Just as funny thing, are there some dubs that saga3 is based on sage2 engine??