It was a suprise to me when Broad was given the captaincy but there were not alot of candidates other than those you mention. Since he was given that he has behaved slightly better on the field and i've noticed far less moaning and poor body language towards umpires. Andy Flower may have hoped for this when he gave him the chance. He is also likely to be around in the Test side for the foreseeable future and any leadership experience will be a positive for England in the long run.
Pietersen is unlikely to captain any England side permanently again after what happened when he originally had the main job. Morgan may have been the only other real option and he is the VC so may get the chance after Broad. Bell would've been a candidate had his place in the side been secure i'm sure.
For test Strauss is a top man, would say he is even better than Cook to be honest.
I hope Board improves his body language and behaviour, I don't know whats up with him but he looks immature and idiot. You see Cook and then Board you say what is this? Cook is probably if not the nicest person in England's side, never ever seen him in any problem since he made his debut.I have high respect for that man.
I think Cook still has another 7-8 years in him
(at least) as he is only 27! Strauss is 34 and he might play for another 2-3 years so after him I'd give Cooke captaincy. He is probably best man for the job, better than Bell too imho.