Re: Changing the Blogs Creation Function**
This is a WPMU issue and not a BuddyPress-related one.
There are some great WPMU plugins by dsader that limit the WordPress backend:
I suggest checking those out.
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[EDIT]
Just read over your post again and you say you want to eliminate the entire backend? Off the top of my head, I don’t know if that’s possible.
I don’t think anyone has attempted this in BuddyPress yet, but I could be wrong.