You sound skilled enough to watch the IP's and see the current patterns. Yes, AWS features prominently as secondary validation sites. They have plans to add a 5th validation farm soon. The primary is not AWS (today)
They have always coached that their IP's can change at a moment's notice. They are looking at adding a different provider. Their have been other substantial changes. If they were to publish these they would want to automate alerting of changes or developing an API to publish them. I am certain that at least some firewall operators would not react promptly 
So, just trading one set of problems for another. Possible expansion of surface for attack as well.
They need reliable comms from all their validation sites so I don't see them using any of the countries you mention any time soon.
These are my personal thoughts not at all official. For some official extra info see below post and even that whole thread.