Disabling NAT

I have an R6400 Nighthawk, and I'm trying to use it as a router/gateway/dhcpd, without NAT, so that the wireless hosts and hosts on the WAN network can all talk to each other by their respective IPs. I looked at the "Bridge" settings, but it seems this is only in reference to connecting wirelessly two wifi routers. I also looked at the VLAN/Bridge settings, but every time I try to enable VLAN/Bridge, the router becomes completely unresponsive after reboot; in that no communications can be made the router over wifi, the WAN port, or any of the LAN ports. I have to restore the device to factory defaults if I have any hope of ever contacting it again. I even played with static routes in the hopes of getting it to work, is the R6400 not able to simply be a router between it's wireless network and WAN port? There is the AP mode, which I think might do what I want, but the Nighthawk will then grey out lots of features. Routing features, DHCP services are greyed out, restricting connections by MAC address, even traffic stats are greyed out as well.