Sounds to me like you have a pretty good idea of what you are up against in migrating the BES to a VM environment. The dedicated SQL scenario could probably be converted to VM or even co-located with the Bes VM for further efficiency, But that is a matter of personal preference with the number of users you have. If your company has rapid growth potential, this would seem to be the opportunity to build in a bit of Disaster recovery if you have not done so. The one other thing I would point out, is to do the knife edge cutover first then perform the upgrade in the standalone environment. just a lot less grief is they are treated as separate events.