I thought one of the advantages of BootMii was to be able to access the system flash even if the Wii was bricked?
"Inserted into the boot process, BootMii provides you with a "safety net" -- you can back up your entire Wii to SD in under three minutes! If you were to brick your Wii, BootMii would still run and let you restore your backup from SD, quickly and painlessly."
http://bootmii.org/about/