1. Of the four players you mentioned, I doubt very seriously you could get a 1st round pick for any of them. Maybe if you bundle a couple together, but otherwise, very unlikely.
2. I mentioned Witten as a possible trade candidate two years ago. Now, he's too old; same with the other 3, for the exception of Dez, whose off the field issues will likely scare away trade partners.
3. 8 and 8 doesn't mean scrap the team.