Well... I keep thinking that Cap's Super Soldier serum would have regenerated the damaged parts of his body. Remember back in the 90s Cap's serum was wearing off and he was dying for a while... the ugh... shudder shudder "RoboCap" time. Now he had the serum basically rebooted then. So its still technically "fresh" in his system, and maybe them throwing him in the ocean in a block of ice was the smartest thing they could do, since it would preserve his tissue and allow the serum to gradually work on the damage.
I think Cap never truly died. Sure he "died" but he didn't completely go away... and heh who knows maybe Heaven knows that Mephisto fucked up the MU and y'know what they don't want Osborn and Mephy screwin' up the MU any more than it is, so they sorta keep Capachino in a "holding" area until he's ready.
Then... Cap busts out of his coffin, takes a couple of days to warm up... fuckin ocean's fuckin freezing doncha know? Then goes and stops RoboSkull and shoves his mechanical arm straight up his ass! Not literally of course.
Then goes and shoves Norman's glider up his ass... literally.
Then, takes the Patriot armor and takes over HAMMER, with Bucky's help whups ass. Takes names. And then takes over the white house booting out the skinny black dude! Hey it could happen.