I gonna answer that in my experience, since no one from the HM team answered so far.
I understand you are expericencing some trouble about saves from different versions.
If you have the asian version (not sure about which version would this be... CH/AS or JP), you can't get any of your NA saves, because PSN understands Alienation from different versions/regions like disctinct games, even if in they are the very same. If you copied your save from console to a flash disk or an external HDD/SSD, you noticed the directory of your backup save would have some of these product ID's in its directories:https://www.gamefaqs.com/ps4/827530-alienation/data
In order to get what that means, you can play the US/NA version, but your save will be registered as (root)PS4\SAVES\(userID)\CSUSA-04181\(save).
If you get a new account from another region on your PS4, like the European (EU) account, you can play the american version with no problems. Your will have a new save in the same directory (CSUSA-04181). But if you get an European (or any other region) account which you were playing with Alienation that wasn't the US version, you will have a different directory on it. Even if you try to copy a save from a US save directory (CSUSA-04181) to a european save directory (CSUSA-00062), it won't work, because when you're about copy it to your console it will say that's corrupted data.
So far I've noticed you won't be able to do that because you don't have the same PSF key even if that's from the same user... even if you just delete your save, you new game will have another new different hexadecimal data for this brand new PSF key. Plus, there's the encryption from Sony to PS4 files, making the possibility of merging saves from different regions kinda impossible.
I've tried a loooooooot of things, but I don't think there's any chance to make this happens.
Plus, I'm stuck with the idea of having a 12-slot SMG with boomerang on shoot in Hardcore mode, but nor me or any other accounts managed to find such weapon on US/NA version of Alienation. I've started to talk to people with american flags I've found on leaderboards or map and not a single one managed to get it, but I've found more than 10 guys who got it on european version of the game... oh, the irony...
I've even suggested Housemarque to put some price on weapons so we could get 12-slots that we keep looking for over a year and have no success on that, but I gave up the idea.