@cunnie Nice article 
I disagree with your recommendation to use the Google time smearing servers as upstreams for your NTP pool servers.
There is no doubt that using EC2 to serve NTP pool traffic is one of expensive ways to contribute.
As you’ve pointed out a cheaper option is to use a VPS provider that offers full virtualisation to use in contributing bandwidth to the pool:
Linode
Digital Ocean
Vultr
BuyVM
Ramnode
LunaNode
Atlantic
Arpnetworks
We do need to be mindful of the TOR “problem” where contributors to that project are largely centralised among a few networks, and yes it would be far better to have lots of people contributing with smaller “net speeds” from home connections with static IPs.
In summary there are cheaper ways to contribute bandwidth to the pool than using EC2