The problem with that is Joss knew the writing was on the wall extremely early in Angel's 5th season.
Currently the writer are working on what episode 18 & 19. That leaves three real episodes to plan closure for a series. That leaves very little time to "take risks". Since the actors only took a one year extension, I think it would be easier to use that (or if they had been told early in planning for season 6 that it would be its last). But once the ratings came in, thats was pretty much not going to happen.
As for the character beats, yeah they do repeat, but thats human nature. And I don't think Dean had ever gotten to the point where he wouldn't try and take care of his brother. He might treat him more like an adult able to make his own informed choices. But that doesn't mean he wouldn't try and shield him still from the worst of the things, or protect him from things that he truly doesn't understand.
I mean Dean right now is trying to shelter him from his own Hell experience. Something Sam doesn't have any memory of. Dean has his own experiences which weren't as bad, and knows what that can do to some one. Sam can't make an informed choice on that issue, as he has his memories wiped. And until he has the memories that can even match the 40 years that Dean went through, he can't accurately assess the situation.