there are two files... BOOTFLOWOUTRO.vp8 and FIFA_ATTR.vp8 (the latter is the one that goes automatically if you wait to press start ..
of course your videos must be converted in vp8 format... easy to do with CG File Expl
But if you want the movies instead of the skill games while match is loading you need also tho change the file in data/ui/nav folder... now I don't have pc with me so I can't tell you more..
Also could you possibly share your .bat files when you're able to please? This would be a huge help. Technically, could the same be done for player appearances? For example, players like Pogba or Neymar who change their appearances often. So if you want a specific look for that particular match, you simply run the .bat file for that appearance file set, am I seeing this the right way? Could regeneration be worked into a .bat file also

?? This would be exactly what this game needs, more innovation/automation when it comes to mods.