Wave had revision control. You could roll back. It might not have been a perfect implementation but it was there.
You could create groups, add them to waves, and have them notified through email. It again wasn't that friendly/easy, but it was there.
You could kick people from a wave. It wasn't there in the early versions but was implemented and working in later revisions.
You could allow people read and/or read/write capabilities. This too wasn't there in the early versions but was implemented in later revisions. It worked. This isn't a wide list of editing permissions, but they were there. One of the complaints about Wave was that it was too complicated. Want to make it more complicated--- add complex work flow and privs. At least this part of Wave was simple.
If you just used it as a collaborative work tool it wasn't even that confusing. I never saw anyone when invited to a wave struggle to participate. They could come in cold and manage to participate.
You are right that Google got the "why" wrong. It was an incredibly effective small workgroup collaboration tool. I don't think that was the niche that Google thought Wave would fill. Regardless, it worked great for this purpose, and really was the killer app.
It's nice to see so much of Wave making its way into other Google apps. I wouldn't be surprised to see Wave come back in some new form within the Google Apps. The early versions of WiaB is really quite simple to use, and shows promise as being Wave done right and with focus.