I'd like to configure a site to site wireguard connection between two OpenWrt VM's.
But I'd like to do that in my office before I haul one of the hypervisors out to a different site.
Please see a screenshot of the current situation and the intended.
I'd like to simply plug hypervisor 2 in on site 2 and things just work directly. Can this be done and if so what should I take care of?
You can setup the wireguard tunnel as usual. Create the server and client configuration. Then you'll add the routing for the lan subnets to achieve the site to site tunnel. For the first part you don't need much on the firewalls, only to allow the incoming traffic on vm2 wan firewall. When vm1 is migrated to another site you'll need to allow incoming traffic on its wan zone and make sure that one wan can reach the other, maybe ddns will need to be utilized in case of dynamic IP.