if you're going to sack someone it's as well to have some idea who you would like to replace that person.
I hope you don't mind if I disagree with you there.
2 reasons really; generally speaking, they're different decisions. Whilst one will necessarily follow the other, they should not influence each other. That is, whether Terry should be sacked or not is one decision to be taken on it's own. That there may be no suitable replacement ought be irrelevant, it does not change what Terry has or hasn't done.
Secondly, and more specifically, I'm not sure it should be left to the FA to decide who is captain. I'd doubt whether some of them even know who's in the team!
