Yes this should work as long as you update the vCD agent to the 5.5 version after vCD is upgraded.
I did this a few weeks ago with another customer, only because they wanted to compartmentalize the upgrade process. Do vCD + vCNS first, then vCenter, then ESXi. E.g. make minimal changes and test.
Chargeback I am less familiar with right now. So long as Chargeback states it will support vCD 5.5 and vCenter 5.1u1 on the matrix, i don't see an issue with that either.
