I'm using OSD for bare metal installations, on both physical machines and virtual. I'm honestly not sure how well it would fit in together with Server Automation.
Generally with offline image patching, it involves creating a VM from a template (including a preconfigured virtual disk), updating the patches, and then saving the modified virtual machine as a template. New virtual machines would then get provisioned using the up-to-date template (either a Sysprepped image, or IIRC VMWare has its own kind of "mini-sysprep" used in VDI provisioning).
I'm pretty sure SA has pieces to deal with all of this, but I'm not sure where OSD would fit in.
The OSD pieces deal with running sysprep, capturing to an image, uploading the image via the BES Console, and then creating deployment templates to deploy the image to new machines. Deploying the image over the network from the OSD server to the VM would certainly be a lot slower than cloning the VM from a preconfigured template. And virtual machines, being identical hardware, would not benefit much from the things that OSD brings to the table, like driver management, personalization rules, etc.
Certainly open to hearing more on this, and honestly I don't enough SA experience to speak with authority on this, but there's my 2cents anyway. Take it for what it's worth.