> Being able to use Arch Linux or Debian, and the latest mainline kernel and have replaceable storage is just so much more flexible in what you can do.
Why not use dedicated router/firewall software like pfsense, OPNSense, or Untangle (all BSD-based, Untangle is a paid product though)?
I bought a little NUC with an Intel CPU and NICs to run pfSense a few months ago and it's been fantastically stable.