Right now I have my router setup like so:

WAN - Fiber connection to internet - X.X.167.114/30
LAN - servers and colocation (public IP addresses) - X.X.49.1/24 and X.X.59.1/24
WLAN - WISP network (public ip addresses) - X.X.196.1/24

I have DHCP running on the WLAN interface with only allowed MAC addresses being able to obtain an IP.

I'd like to change this a bit and hand out an internal NAT'd IP address to unknown MACs. I then want to redirect them to a specific website with my company information on it.

How can this be implemented?