HyperV on Domain Controller or DC on HyperV

If you are building a Windows environment, run a Windows domain controller. You will save yourself an infinite number of headaches and drastically reduce your setup time. Plus if/when something goes wrong competent MS folks are easier to find than competent *nix folks with domain controller hackery experience :)

You can run a Domain Controller on a very lean system (or even a VM as you mention above) IF you resist the temptation to tack a bunch of other services onto your DC. Running WSUS on it is probably OK, but It should NOT be a git server and it should NOT be a development machine. Dedicate another box for these tasks (it can even be a unix system, which will make git easier to wrangle).
ideally nobody should be logging in to your DC locally, especially in a lab-type environment.

If you are not married to using Windows clients there are a number of ways to implement the lab environment using BSD or Linux systems...

The short answer is SCVMM.

It's a product Microsoft makes for expanded management of Hyper-V VMs, however it has a very nice web portal that can have permissions delegated down to the individual VM level if desired. Start, restart, pause, and Snapshot are some of the capabilities that can be delegated. The one you're most concerned about is Console access through RDC and it can be allowed through the web portal as well.