There is no supported upgrade for Hyper-V and I share your love of Hyper-V and disappointment that they are so fixated on VMWare. Although it isn't supported Hyper-V will run just fine with the 11.1 SP1 and above versions.
I have many clients using Hyper-V for VM Pro linux and have had no issues after the service pack was released for 11.1. The initial version had to be restarted quite often. I love Hyper-V because I can save images, run windows backup, and have regular full backups with my normal server software as well as cloud backups with Acronis.
My procedure is to install the new Hyper-V linux, get it setup but have it on a vlan so it isn't active. Then run a backup on the old Hyper-V instance, use WINSCP to copy the backup to windows server, then shut down the old instance. Turn on the new instance / remove vlan and then restore the backup to the new instance and it is up and running.
The backup won't bring over the vm to email server settings, so that has to be put in after the backup is restored. If anything goes wrong you still have your old Hyper-V instance and it's a snap to revert.