Got to say, I disagree with a lot of this:
Punk has simply never been in a position where it would have been logical for him to main event wm. I have to disagree with that one. Honestly I wouldn't see any issue with Jericho/Punk being the main event at WrestleMania 28, in fact I feel it could have been the perfect time to do so. Punk was still riding the waves of his shoot, and Jericho was pretty much at the top of his game (or as much as he could be at the time). It was before WrestleMania 28, that Punk really took off, so logically, WrestleMania 28 would have been the perfect time to do it. Punk/Undertaker could also have been a perfect time. WWE could have easily booked WrestleMania 28, with Cena winning rather than Rock winning, that was the perfect time to pass the torch over, have it be over and done with rather than leave another years worth of build-up. That could have easily left things open for a possible Cena/Punk main event at WrestleMania 29, with Punk holding onto the title, and Cena winning the Royal Rumble. Of course that would have also meant possibly finding someone to fight against Undertaker. But in the case of WrestleMania 29, it made sense. Punk would have walked in the longest-reigning champion in years, go up against Cena, and adding to the fact that these two had history, would have made the match work even more-so. I honestly, see things working better for Punk at either WM28 or 29, I'd probably say 29 was the best option, what stopped that and Punk's momentum cold around that time was losing the title to Rock who moved onto Cena, leaving Punk left with a pretty shakily booked storyline with the Undertaker.
There are guys that have had better careers than Punk and never Main evented a Mania, or only main evented once and it was at the end of their careers. Honestly, by this kind of logic Miz shouldn't have been anywhere near the main event then. How many people have honestly had better careers than Miz? Think about it? How many of those people were probably wondering why Miz was there to begin with. I won't deny that Miz might have been hot around that time, but main eventing WrestleMania? Even against Cena? That's way off. Around the 2011/2012 period Punk was pretty much hot, he had just about every reason going for him to main event at WrestleMania.
Punk needs to realize that he has only been relevant for two maybe three years and half of that time he has been irrelevant and hasn't done anything great for the WWE. Edge, Jericho, and Foley have all only closed the show once and imo they were all relevant longer than punk, gave us more legendary moments than Punk, and had better careers than Punk. Outside of Cena or Rock, during those two-three years who was more relevant? I mean, obviously, Cena and Rock are going to be the main attractions when they are around, but everyone else, out of everyone else, who was really more relevant than Punk at that time? Outside of Cena and Rock, who made some kind of impact during that time? You could definitely say Brock Lesnar, but keep in mind he was a part-timer, Punk was on just about every week. But outside of that, anyone? Bryan is definitely a possibility, he started to pick up steam around that time as well, of course, he ended up going to the tag-division, but he still held onto it during that time. But outside of that, in that realm of time, who around the main event scene was more relevant than Punk, outside of The Rock and Cena? Being relevant longer doesn't really mean much, unless you have people you're competing with, around that time Punk was competing with two main people, Cena and Rock, yes Bryan and Lesnar both could be argued, but again, neither of them went much of anywhere, Bryan got regulated to the Tag Team Division with Kane, and Lesnar, had a match with Cena, then worked out a feud with HHH sometime later.
And hasn't done anything great for the WWE? His shoot alone put him on the map. The match at MitB with Cena was pretty damn great in general the whole "Summer of Punk", he was on fire, his time after that was going great (until he went against HHH which pretty much killed his momentum), having the longest Championship reign in years, a 5-star match with John Cena and a match with the Undertaker. Honestly, does that sound like a guy that doesn't deserve a main event shot at WrestleMania?
Even if Batista never signed Punk still wouldn't have been in the main event. Debatable. Punk and Bryan both had a shot of going against Orton before Batista came along. With how far Punk made it into the Royal Rumble, it's very possible that either Punk or Bryan could have picked up a Royal Rumble win and went on to headline WrestleMania. Going by the crowd, Bryan could have probably picked up the win and been on his way to the Royal Rumble. And Punk (who was likely to have been involved in the Elimination Chamber, could have actually won it). Probably wishful thinking on my part, but without Batista, I think either of them could have made it to headlining WrestleMana, or even both. Punk is very well at the tail-end of his career. Whether or not his contract expires and he re-signs depends on him. Now could have been another perfect time to have Punk main eventing WrestleMania.