Assuming he's fit, got to be Peter Murphy - during his short appearances, he led the team very well indeed.
I don't think we should have a fixed vice-captain. Beeley has been woeful this year and his leadership (or lack of) has contributed to the poor performances in my opinion. I presume Jim made him vice-captain as a consolation prize in the anticipation he wouldn't be needed and that PM would be the captain, and has been stuck with his decision.
Let's see who Jim brings in during the Summer - a new central defender is almost essential, so the new guy could well be the next substitute captain when PM isn't on.
I agree Kenyon is turning into a mature player, but probably still too early for captaincy - it's not just about motivation and who can shout loudest, it's about strategy, so you need a thinker. (So that rules out Flemmo
)