NetFlix doesn't need 4.3. It has been out for ages, and so does not have 4.3 on the disc. You simply have a missing or outdated IOS.
Anyway, there is no 0.6 or 0.7 of BootMii yet, the latest is 0.5. There is a
HackMii Installer 0.6 and 0.7.
As for the what you were talking about restoring NAND dumps...a dump taken on 4.2 with BootMii 0.4 (installed with HackMii Installer 0.6) can be restored without issue on 4.3 with BootMii 0.5 (installed with HackMii Installer 0.7). If it couldn't, it'd be a pretty bad update.