If any regional Govt were to seriously consider providing "marketing support" to FR for a year or two, presumably they would by now expect this kind of reaction when the money runs out, and thus factor it in when doing the original deal before any payments begin.
In other words (numbers are hypothetical)
We think that paying 1 million euros per year will encourage the development of 5 new routes. But we know that FR will make a huge fuss in 2 years time when payments end, so we'll ask for 8 new routes for the money. In 2 years time, we expect 3 out of 8 routes to have failed, so we still get 5 new routes.
The result is that the local Govt doesn't have to get the choice of routes exactly correct - they leave it to the airline and passengers to decide. The local hoteliers don't care *where* the new tourists come from as long as it doesn't cannibalise existing air routes too much, just that they come