Whilst I agree with you on everything you say about Fyfe (he's the heir apparent to my affections when the sad day comes that pav retires... that's after I've safely been taken off suicide watch of course), but he isn't in the leadership group either. MdB has been there since he was 20 or 21 so presumably it's not an age thing.
Sandi and McPharlap as the two main deputies are clearly too old; MdB is not a good enough player; that leaves Mundy from the current leaders who have done a reasonable appreticeship in the leadership group, shown loyalty over their career, is an outstanding player in his own right... Maybe Mundy as an interim until Fyfe is ready?
I'm not advocating Mundy particularly, but Mayne, Johnson, Ballantyne, Ibbotson have been in and out of the group - and none of them scream 'captain' to me... and neither Barlow nor Fyfe have been in the leadership group at this stage, although I think one of those two would be the best candidate from the outside looking in. So really, that leaves Mundy in the short term IMHO...
Of course, I could be waaaaaaay off the mark. Wouldn't be the first time.