The solution turned out to be leaving the FQDN field empty. (I was previously putting "vsphere.local" into it, to match the hostname.)
Leaving the field blank causes the FQDN to be autocalculated as hostname-else-IP (depending on rDNS, per the field's hint), and will therefore work on all of the following:
- Statically addressed networks with reverse DNS
- Statically addressed networks without reverse DNS
- Dynamically addressed networks with reverse DNS
(I'm unclear on what the appropriate setting is for networks that use dynamic addressing and do not have reverse DNS. I suspect that, in that case, forward DNS becomes a requirement, and the vCS' resolveable hostname should then be entered as the FQDN, but I cannot confirm this at this time.)
It's worth noting that entering the IP directly into the FQDN box (per André's suggestion above) may provide a slight speedup during installation, for networks that use static IP addressing and do not have reverse DNS. I'm unclear on whether doing so will introduce additional complexity during re-addressing, if IPs are changed in the future.