Wow. That's a lot of thinking! My brain hurts for you... I really like the idea of Dean being the vessel for Lucifer -- and I totally can't believe I just said that! Cuz. yeah. check out my username... I like the thought of that being the purpose heaven had in mind for him so he could totally off Lucifer from the inside. It would make sense, then, for Uriel to want Dean dead if he was going to host Lucifer only to kill him -- I know, I kinda modified your thinking a bit -- but heck! You've totally got me going here!!!
Great ideas... though I do like the idea of Anna giving Dean angel powers...