The objective would be to provide equal services, equivalent to those of the organization that administers the IELTS test in English, worldwide. There are similar tests in English, such as the TOEFL, which is very popular in the United States. At a certain price point, this would probably be possible. Those tests are administered in hundreds of cities throughout the world.
If there were testing centres in hundreds of cities worldwide, including countries where there are few francophone candidates, the unit cost would be very high. It's not that the government would be unable to do it, but that the cost would be enormous.