Ok, I think I understand what you are asking.
Yes, you can set up a router - router VPN, as well as have a router act as a VPN and have software clients on remote PCs access it. Similarly, you can have a software based VPN, such as OpenVPN, on your camera server which will work with pretty much any router, as long as you forward the port. I would recommend looking at the Cisco routers if you plan on having a lot of traffic. For a smaller application, Netgear makes some VPN routers too. In essence, you would have a small lan for the cameras and camera server and then when someone connects to the VPN, they would have access to the cameras.
In your diagrams, you show the cameras, the server, and clients all having a 192.168.2.x address. I assume this is through the VPN. One other option, depending on your architecture would be to put the cameras and camera server in a VLAN and then set up an access control list (ACL) of who is allowed to access it. In the previous place I worked, this is how they set up the security cameras.