Currently, there is no way to restore your vWii NAND with a homebrew.
He only needs to restore IOS58 (most likely)
That should be doable through wupserver/ftpiiu everywhere (on the Wii U side)
I see people having bricked/semibricked vWii quite frequently here and I always suggest that method, but I don't really know the details (what files need to be copied, any permissions that need to be set) nor do I know if anyone suceeded at fixing their vWii this way. But theoretically it should work.
I thought of launching a WAD manager through an exploit game to restore IOS58, but that won't work because the exploit games don't have the AHBPROT access needed to overwrite system titles.
Doing it from the Wii U side is probably the only way.
Edit: Actually a WAD manager may work.
@Kamesennin do you have cIOS installed and an exploitable Wii game?
If so try to run a WAD manager through it by placing the boot.dol/.elf on the SD root and running the exploit. Tell the WAD manager to use IOS249 (or 250, or 251, or 236, whichever one you have should work) when it asks.
This is the best WAD manager to use for vWii as it has some vWii specific patches:
https://sites.google.com/site/completesg/how-to-use/wad-manager/YAWMM_EN.zip?attredirects=0&d=1
If that works, you have to get a clean vIOS58 WAD and install it. You can't make a good vWii IOS WAD from a NAND dump but if you have a full vIOS dump from when you hacked the vWii (made with a tool like bluedump) then you can use that.
If you don't have a dump of vIOS, you have to get it from someone else, as good vWii IOS can only be gotten by dumping them directly from the console. Maybe there is a vWii IOS dump online somewhere (google) but if not you will need someone to send you the clean vIOS58.
Don't use a Wii IOS58 (that's probably what got you into this mess in the first place)
If you DON'T have an exploitable game but you DO have cIOS, follow the steps above but instead of running an exploit game you can use wuphax (likely the same way you installed HBC in the first place)