BuddyPress.org

“Member blogs come up, but each new member would have to configure their own widgets.

I’d like members to be able to join and have everything set up for them. “

this comes up under basic WPMU blog defaults, and is covered extensively over in that forum. there’s even 2 plugins available to set blog defaults.

with widgets it’s a little different – if you don’t want them to change anything, don’t use widgets. hardcode it in the theme sidebar.