It is indeed possible to play a save on another account, but you will have to put the save on to a USB stick first, then using a PC unlock it and edit it, resave it to your USB then copy it back on to your PS4. This is bad advice though, as it may lead to your account being banned if you play online. If you don't you shouldn't have any problems.
I won't tell you what software to use to unlock it and edit it, but as usual google will.
Sony used to allow us to make our own themes, dynamic and all, and they did have their own save editor too. Perhaps they will still work.
But, apart from that, I'm not sure how you can do it anymore.
surprisingly the PS3 allowed for so much more than the PS4 ever will.