Been there have a 30 gb jdm image sitting here . Hdd tools will pop the lock off . MHDD will disable it. From there I hit it with a hex editor and shortly after left it for some thing else. The thing to realise is this is a different box to what t other cars have. There is a TV tuner to control, e card reader to control and a traffic mgt unit to control . All of that has to be tied into the main code somewhere so a literal dump of a English unit will not boot in a jap box. Already been there with aftermarket units . Both of those ran windows industrial but they were different enough internally that the system would not boot at all.
If you do decide to unlock and image one you won't do damage IF you do your homework before hand.
The toshiba unit used in these is there for a reason . Automotive grade unit capable of taking more abuse than a standard drive. We all know the standard drive can take a fair bit , these take more again.