I do plan to eventually make the SG-1000 my primary router for myself, but currently I have a lot of special configuration on the router that I don't want to replicate and I don't want the "production" network to go down if I screw-up the SG-1000 configs.
Also, I want to have the option to use SG-1000 as an "OpenVPN appliance" that I can just "drop-in" to client networks by having it completely pre-configured. The LAN port would get an address by DHCP, so the only configuration I would have to do is define a DHCP address reservation on the foreign/main router and add one port forward to it and then the SG-1000 would just be a "plug and play" device to add a short-term inbound VPN to the network. A "keep in the toolkit" and deploy so I could minimize time onsite and do the more advanced network administration (of the other stuff, not the SG-1000) via a secure remote access VPN. (Theoretically, I might even be able to FedEx it to a client and talk them through the minimal installation without a physical trip.)