Voting for the location of the CIS-2107 tournament.

But if expensive internet is needed for streams, why can't this issue be solved the way I suggested?

You seem to be missing the point. For streams and just for communication in general, you simply need a decent internet connection. But at countryside venues, it is by definition expensive. Because the Wi-Fi, on which you can barely load even a single page of the HeroesWorld forum, is not internet — it's a mockery of it.
Conduct a poll among past participants: whether or not normal internet is needed at the CIS venue. For me, for instance, it is needed because I can be called for work at any moment. And there are plenty of others who can be called for work or other matters.
And phone reception, by the way, is not always reliable at countryside venues (3G and 4G are also not always available accordingly). This is, if you will, the nature of the times. The internet is needed not for streams, but first and foremost for the participants and viewers themselves.

Added after 2 minutes

As an option — you could pay for the travel and accommodation for top streamers (for those who need it), if there is some guarantee that the money can be recouped. Sort of like issuing an advance.

If you find streamers who will give you such guarantees — go ahead: pay up, issue advances...