This was just posted by Reddit user luthia at:
https://www.reddit.com/r/ffxiv/comme...ttime/dj5es18/
I have not tried this, so I cannot confirm. Just reposting here in case someone wants to.
"Ok, so for those that have a back up HDD, I found a quick fix. After you're done downloading the 22GB file, use the backup/restore function in your PS4. The less content you have, the faster it will be. Having an SSD will probably make it a lot faster as well.
Now continue playing as usual. If power goes out again, simply go to the backup/restore, and restore your files. Voila! You now dont have to re download the big ass file.
I just did this last night, because I live in an area where power goes out on a daily basis, and this morning, power went out. Restored from my external HDD and was able to log in just fine"