Configure it like the current router and keep it as a backup?
You can run a lot of stuff on it, but those boxes aren't really that powerful... a cheap, old raspberry pi from ebay (or anything really) will serve you better.
Hey! I just got one of these at a thrift store the other day for a couple bucks.
If you want to mess around with pentesting your own devices, there is build based on a specific version of openWRT compatible with it that will let you turn it into a wifi pineapple and it works quite well. Because of the USB ports on the back, you can plug in an additional wifi dongle to add another radio and make it more effective for that.
Here is the repo for the pineapple software based on a specific version of openWRT:
The c7 has a usb with enough juice to run a 2.5” external enclosure if memory serves. You need to link up with the portable file server person and form up.