There is no real downside to 4.2. The act of updating will overwrite BootMii/boot2, but it can be reinstalled after the update. The update will also overwrite any IOS with the trucha bug, but again, you can patch trucha bug back into IOS36 with Trucha Bug Restorer or dop-IOS MOD after the update and you're sweet. My advice would be:
i) download HackMii Installer 0.6
ii) Use it to update HBC and DVDx to latest versions
iii) Do official WiFi update
iv) Use HackMii Installer 0.6 to reinstall BootMii (latest version. BTW, WiiMotes are not supported and probably never will be. Its too low level)
v) Take a NAND dump
vi) Use Trucha Buge Restorer to downgrade IOS15, patch IOS36 and then upgrade IOS15 again
After that you will have a fully functional 4.2 Wii. BTW, because the update overwrites boot2, it is slightly risky. However, this is only if you lose power at wrong moment. Because BootMii is overwritten, if this happens, you have no way to recover your Wii. However, provided the update completes succesfully (which is the most likely course of events), your wii is safe.
EDIT: Alternatively, accept the update on the disc and BootMii will not be overwritten and there will be no risk whatsoever, as BootMii will be there to protect you. And you can use WiiSCU or dop-IOS MOD install IOS61 and the latest Shop Channel.
Edited 1 time(s). Last edit at 01/04/2010 11:10PM by SifJar.