Use Tetra as wifi hardware firewall?

[Madbison]

Is it possible to use the Pinapple Tetra  or Nano as a wifi firewall? Connect the Nano to a public open AP, and block ALL incoming traffic from the public AP. 

I have seen that I can go through the public AP sign-in process with the laptop, having set the MAC address of the laptop to the MAC address of the Tetra. Then the Tetra should connect to the public AP. 

I can then connect my laptop and phone to the Tetra and have internet access. I see I can also limit access to only Mac addresses of my own devices. The real questions are:

1) does the Pineapple provide secure login option for me to get the guest interface, or is that always open?

2) does the Pineapple provide firewall features in this case? Stop any device on the open wifi AP from seeing or attempting to communicate with my phone or laptop in any way. 

I use a VPN which makes sure all traffic is encrypted against snooping. But connecting to public wifi leaves my laptop and phone vulnerable to potential attacks form other AP users that I would like to eliminate.

Thanks!

[Forkish]

The tetra is an OpenWRT box. So just about anything you can do in Openwrt, you can do with the tetra. It would just take some sweet iptable-fu. Also, if you’ve got physical access to the wan box, the rj-45 is input only so you could hardline it to help cut down on the frequency traffic.