Having achieved the important goal of the bootloader access and modify files residing in the NAND memory the XDA community few hours ago has released the first Custom ROM for Lumia 800 and Lumia 710.
The custom ROM is based on new firmware 12070 (RM819_059P453_1600.2487.8107.12070_002) and integrates the Interop Unlock, but unfortunately can be only flashed on Lumia 800 and Lumia 710 with unlocked bootloader (available only in the first official firmware).
Now the XDA community will work to make the ROM available on all Lumia devices, trying to open each version of the bootloader.
The flash ROM requires custom tool 'dd' (pre-installed on Linux distributions installed on Windows) and u hard reset the device. If you are interested will find information on Xda-Developers.
More information can be found at Xda-Developers.