For bypassing carrier restrictions, one could simply use termux + tinyproxy.

pkg install tinyproxy

cat > tt.conf Port 8888 Listen 0.0.0.0 Timeout 600 #Allow by default allows clients with any IP

^D

tinyproxy -d -c tt.conf # -d means no daemon

and whatever you fancy on the client side.

The trick is to disable WiFi internet and use data on a phone and then connect to client's hotspot, so client can use the proxy on the phone.

Is there is an option to scale it? I have 20 devices now, that are using iProxy