Sorry no. That is correct the MX250 and 450 only have SFP+ WAN1/WAN2 interfaces for maximum flexibility of 1/10G copper or fiber handoffs and they require an SFP transceiver. And the 0.0.0.0/0 default WAN route will always be out a WAN port. You can call into Support to see if there is a back-end option they can enable to allow you to leverage a LAN port on your MX250 as a WAN port, but I'm not aware of such an option. Even if there was an option for such a thing, it wouldn't be a supported configuration.