Well if I can do that in ps3 we can remarry ps4 ic blu-ray in ss by looking at similar lens they match perfectly kem850 with kem860,already tested, just în case it will be possible to decript , then a stage of downgrade.
I have tested before an bd board with lower firmware on phat ps4 units, they asked for that lower fw even if updated, now think is something related there on eid root key. I would take ps4 bd ic and solder on ps3 ss for remarry process I have thought would be easier with eid root key on later fw with new process of remarry on ps3, seems not easy, tested 2500 on 3.40 minversion remarry ic works.
Ps3 ss and ps4 phat have quite same ic and this should be possible.
If I am right I should find an ss with lower fw and exchange bd ic to an updated unit and should have a screen of lower fw on recovery , if possible to update this could work.