It wouldn't be unwise, virtualising DC's as a rule isn't a problem. You have to be careful of where its getting its time from if its on VMware, dunno about HyperV
If you've only got one host, you wouldn't gain much, apart perhaps being able to run a few VM's on there to get the most out of the hardware. I supposed you'd be able to have a dedicated DC and file server and email server etc etc. I'd want to make one of the other VM's a DC too though.