As I've suggested earlier, I'm pretty sure Cook has a big role to play for England in limited overs cricket, and probably a slot alongside an aggressor such as Prior may be the way England go in future.
Cook will rarely go along throughout his innings at a strike rate of around 100, so therefore it is important for him to provide the solidity at one end, but ensure he rotates the strike, puts the baa ball away, runs hard between the wickets, and quite importantly make some big innings. Eating up a few balls early in his innings is acceptable should he go on and make a telling contribution, not if he is then getting out for around 30 off 60 balls.
He is not a dasher and should never play as such, his strokeplay is enough for him to impose match winning contributions, without the need for fireworks. When he gets in, he invariably scores at a strike rate of around 75, which is reasonable, considering the effective players that can then bat around him in KP, Freddie, Prior, Colly, etc.
I also envisage Bell to come in at number of three for a number of successful years.