If Punk challenged Undertaker similar to how Randy Orton did with the intention of stepping up to do something to set him himself apart then him jobbing to The Phenom would be easier for me to accept.
I'd also go along with your line of thinking of why would Taker cost Punk against Cena?
I could see Punk talking sh** about Undertaker at the start of the show only for Undertaker to make an appearance (or just the lights going out with the gong sounding) to distract Punk and cost him the match with Cena.
Re: Miz being the next Flair
Its bad enough he's doing the Figure Four. Imagine him coming out in shiny robes. UGH!