The local xfinitywifi networks in my area work with raw UDP. That being said, I've been to some areas where the local xfinitywifi networks did not, and it reverted to DNS tunneling.
I'm also curious who you are using for a cloud provider, as many throttle/block inbound traffic on udp/53 to prevent DDoS attacks against improperly-configured DNS servers.
As for commercializing/publicizing this, I wouldn't recommend it. Judging from the effective MTU of xfinitywifi hotspots, it seems as though the gateways broadcasting xfinitywifi are establishing an IPSEC tunnel to a local Comcast-operated server. It would be trivial for them to shut this down in one fell swoop by transparently redirecting all outbound traffic on port 53 to an internal resolver.