Tech9
Part of the Furniture
I sent this question to the Firewalla support email address.
Firewalla support won't give you an answer if you can run different software on their hardware... if that was the question. The appliance is manufactured by someone else and branded as Firewalla. I know is runs Ubuntu with their software as application. I'm pretty sure the hardware is reusable. Again - for only $150 I would get one, play with all the options and decide which one fits better my needs. Obviously you like to play with tech. Why not?
You don't have to disturb your current setup right away. Let it run, you play with the new stuff. Once you have what you want - make the new device your main router/firewall. You may not want to look back at home routers. You can have native VLAN support, proper network segmentation, never worry about NAT acceleration again, you may want proper APs with VLAN support at some point later and ditch Asus (or other) home routers altogether.