this is an interesting thing.

What i want: Creating virtual private servers with Windows Server 2008,2012... that will be assigned only IPv6 and anyone can access its RDP even his/her internet provider does not support IPv6.

What i have: Linux dedicated server supporting virtualization KVM/LXC; IPv6 subnet assigned tot he server; server is in other country and i have SSH access only.

How to achieve that? Are there any tutorials that are solving at least parts of this issue?

I know how to
1) install KVM or LXC virtualization (there are numerous tutorials). I would probably use Proxmox as it is free or Virtualizor as it is easy to work with and has support.
2) i would be able to find tutorial on how to install Windows Server on an KVM VPS thru .iso image.

I do not know how to:
1) setup IPv6 networking so i can access particular virtual servers Windows RDP
2) how to access IPv6 Windows RDP when my ISP does not natively support IPv6 (maybe OpenVPN? no tutorial?)

Please if you know about tutorials or can write a tutorial that can solve at least parts of this task, please kindly share. Thank You

here is how to setup networking and iptables NAT rules to forward node IPv4 request to VPSs without their own pub. IPv4s. Here is another tutorial doing same thing.
Here is how to configure IPv6 on KVM Proxmox virtualization, here another tutorial on same thing. And here is third IPv6 setup tutorial.