Hello everyone!
I've tried to re-region saves from CUSA01140 to CUSA01154, but it turned out that there is 2nd layer of encryption. Each file inside the "MGSVTPPSaveDataNA" is encrypted with a different key than it would be in "MGSVTPPSaveDataEU".
Using the program from that repository, you can translate files inside, one by one, and make them compatible.
A jailbreakable console is still needed to decrypt standard PS4 save encryption and encrypt SaveData afterward.
You can also translate your saves to a PC version of the game.
Below is a link to a couple of saves from various regions, that I've successfully re-regioned to CUSA01154.
DOWNLOAD LINK:
Enjoy! 
EDIT: Added compatibility with Ground Zeroes save files, but for this game, PS4 saves will not work on PC and vice versa.
I've tried to re-region saves from CUSA01140 to CUSA01154, but it turned out that there is 2nd layer of encryption. Each file inside the "MGSVTPPSaveDataNA" is encrypted with a different key than it would be in "MGSVTPPSaveDataEU".
Using the program from that repository, you can translate files inside, one by one, and make them compatible.
A jailbreakable console is still needed to decrypt standard PS4 save encryption and encrypt SaveData afterward.
You can also translate your saves to a PC version of the game.
Below is a link to a couple of saves from various regions, that I've successfully re-regioned to CUSA01154.
DOWNLOAD LINK:
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EDIT: Added compatibility with Ground Zeroes save files, but for this game, PS4 saves will not work on PC and vice versa.