Well, first, there exists no Social Login feature, so you'll have to have someone develop it for you. Secondly, Twitter is a micro blogging platform, and as such only allows posts to be 140 characters long, so limiting posts on the UBB to be only that length seems like it'd be a bad idea (just imagine this post you just made only allowing you to do in 140 characters).
I could see a new thread URL being added to a feed, but that's about it, I don't really think that every post being propagated to Twitter being much use to anyone, this is a discussion board software, not really a micro blogging platform.
As for automatically signing a user up for Twitter, that's not really an option, plus I think it's against their authorized use agreement; as such, users would have to create their own account, and again, it'd be a lot of development to remove all of the login/registration/authentication bits from the UBB to force users to have to use Twitter as the only authentication medium.
As for "allow entire forum to be anonymous", you COULD do this in stock by just setting each forum to allow anonymous posting; but trust me, you'll end up dealing with a heartache of a lot of drive by spammers; plus, what happened to using Twitter as an authentication medium?
As for having frames autopopulate from URLs, you COULD setup a custom bbcode to do such a thing, but again, you'll be attracting spammers to your site allowing such a thing.
