Q: Is there any way to configure a Hyper-V host so it can't run more than one virtual machine (VM)?
A: There are no limits on Hyper-V as to the number of VMs it can run, no matter which version. The differences in Hyper-V Server Standard and Datacenter relate to the number of guest OS instances for Windows Server that are included.
But these differences don't affect the number of VMs that can actually run on a host. The number of VMs that can run on a host is restricted by the resources available to a host; typically a lack of resources such as memory and storage will stop additional VMs from starting.
The question has come up as to whether a Hyper-V host can be restricted to running only a single VM. There's no Hyper-V capability to restrict the number of VMs on a Hyper-V host. One option would be to remove the permissions from users so they can't create VMs. Another option would be to use a private cloud implementation such as System Center and create a cloud with a capacity of a single VM.
Ultimately, if someone is an administrator on a host, there's no way to restrict anything they can do, including creating VMs.