Got SCVMM 2012 R2 up and running, created a single VM w/ dynamic memory (512MB-4096MB) and a 40GB dynamic disk. The host is configured for NIC Teaming using switch independent configuration.
I setup a legacy network adapter and boot up to WinPE. The version of the boot.wim is WinPE4, configured to launch sccm. I do not know if it has virtual nic and storage drivers, but I didn't have a problem when creating standard hyper-v VMs in the past (2012, non R2). It downloads the boot.wim, but freezes at the very end when (I'm assuming) it goes to unpack it.
That's a 100% progress bar, and it just sits there. I'm in the process of creating a fixed disk VM, but I doubt that will resolve the problem. Posting here in the mean time in case anyone else has come across this as well.