With that in mind, I ask if people have tried to just change the model in their vendor.bin to DHO924 and see if that is enough for a model conversion? Given previous Rigol cases I think it should not be necessary to flash whole new CF 924 images.
For the first batch of DHO804/814s with firmware version 01.14: yes, replacing only the vendor.bin will be enough.
The issue here is that newer DHO804/814s ship with firmware version 01.00, simply replacing the vendor.bin will cause a 5mV-10mV offset to appear, and it can't be eliminated by self-cal.
Thanks to @hubertyoung, we now have access to SD card images with firmware version 01.14, we can basically "downgrade" the newer scopes back to the state it was in during the first batch, which is easily hackable.
Sidenote: Someone has claimed that he managed to perform the hack on firmware version 01.00, but he refuses to provide the method, so I don't know if there's any credibility to his claims.
I am curious about how the vendor.bin is decrypted, and it seems that you mentioned a method for changing the content of it with the SCPI command? It is certainly interesting.