Johnson is in the ideal position for a captain but his version of leading by example is not so appealing. Unless amassing yellow cards is a good thing.
Despite his experience at Leeds, I would prefer Jonny to concentrate on developing his game rather than take on Captaincy. I am not so keen on attackers being Captains anyway. You need a slightly manic side in attack, whereas a Captain needs calm balance.
I agree Martin/Bassong are the natural choice.