Spent a good few hours last night mulling this over. There are two answers here - what I would do, and what I think the selectors will do - the two differ mainly on the point of whether Cook should be allowed to continue as Captain (I would, as noted elsewhere, stand him down and give Prior a go, probably without the gloves).
There is, realistically, a spine of six to eight players who will, if there are no more retirements, make up the core of the playing group - Cook, Root, Bell, Pietersen, Stokes, Prior, Broad and Anderson - Root and Prior being the two not nailed on. Into that group (because it makes more sense to talk about a squad of 14-15 players than it does a single XI, you need to add two more batsmen, a spinner, a second keeper and two or three seam options.
As regards the batsmen, I think Carberry will probably be thanked for his efforts and wished the best in the future, and I doubt that Compton will be considered again (though oddly, having not thought him quite good enough at the time, I now suspect he was quite harshly treated). Ballance...I've said before I think he is probably a year short of the necessary experience, in part because he has tended to bat too low for Yorkshire, but he may well get one slot, and I suspect the other will go to Sam Robson. Interestingly, Scyld Berry was writing in the Torygraph this morning to the effect that a group of ECB bigwigs, asked to predict our next Ashes line up, all had Alex Lees, who I recommended yesterday, in their top 3s, so there may be a possibility of him coming in later in the Summer.
Spinner. England admitted that Borthwick was not up to it when they tossed the ball to KP ahead of him today. They have clearly seen something that worries them in Panesar, and something that they really don't like about Rashid, and Kerrigan will need to think about how he is going to bowl in Test cricket before he can be elevated to that level again. That leaves Tredwell, who wouldn't let anyone down but is not good enough to be a long term option, or Rafiq, who played barely half a season last year and needs time to mature. Who thinks we might go all seam in the start of the year?
Reserve keeper - this slot is up for grabs. In defence of Bairstow, he has been badly treated by the selectors in regards the amount of time he has spent sitting around between infrequent opportunities. That said, he may need the confidence that comes with time back at his county and runs on the board, though the reserve options are not great - Buttler never really scores first class runs and is a similarly inexperienced gloveman, and Foakes is even more junior. If Prior were to be injured, I wonder whether they might give Kieswetter a go?
Seamers - at least here the options are clear. Finn will come back into the group, and Onions will doubtless be there or thereabouts, though I suspect that Bresnan will become a one day specialist going forward. On top of that, I would like to see them bring one of Mills and Topley into the squad - the idea of a left armer would give variety and both have at least one part of the puzzle about them. JAmie Overton could also get an opportunity at some point.