I wouldn't see the spot going to Kerry, due to the need for a new confirmation hearing for SOS.
Evan Bayh would possibly run in 2016, which would go against the interests of anyone who wants someone else to be a presidential candidate. So it likely wouldn't be him.
There could be similar concerns with Ken Salazar, although there would be a politically useful milestone.
Kathleen Sebelius would be slightly more logical, as a way to inspire more women to support the Democratic party in the off-year elections.
Tim Kaine. Obama originally wanted Kaine as VP.
Kaine was one of the two runner-ups along with Evan Bayh.
I doubt it would be Kaine since this would allow the Republican Governor to appoint a replacement. And there would likely be a special election at some point. In those, the demographics favor Republicans, who also seem to have a stronger bench in the state.
Would Anti-nepotism laws applied if he picked Michelle?
I don't think the Pres & VP can be residents of the same state. That's the reason Cheney changed his residence from Texas back to Wyoming.
That's only in elections.
Electors are not allowed to support a Presidential candidate and a Vice-Presidential candidate from the same state.
Technically, a party could run candidates from the same state. It could lead to complications in a close election.