I disagree with the above comment. If you have a wiikey modchip to play backups, and no softmod installed, you can still use bricklblocker and regionfrii,via your PC, to prepare a backup before use, the IOS has nothing to do with removing the update partition from a disc, or changing the backup's region code.
As such, you should have no problems at all.
NOTE: I have a softmod only Wii so can't guarantee what I have written, but I am fairly certain of it. Why not just try it on a backup, at the very worst it'l cost you one blank Disc, but I really do think there shouldn't be a problem. Unless I'm misunderstanding what you are asking ?!?
Good Luck