This probably sounds crazy, but I think the best way to incentivize food production laborers is to pay them a fair wage.
Rural areas have a mix of the estates of the top net worth individuals and the laborers who work there. The wealthy are subsidized along with the working class. It makes more sense to stop subsidizing the rural areas entirely and then pay the working class fair wages.
As for defending the rural areas with force, that's the whole point of having a national military - it's not like we're going to forcibly conscript everyone just because they happen to live in the region.
I don't know about France but in the US the number of high net worth individuals who live in rural areas without making their money there (e.g. big farm owners, mine owners, etc.) is very small.
Rural areas have a mix of the estates of the top net worth individuals and the laborers who work there. The wealthy are subsidized along with the working class. It makes more sense to stop subsidizing the rural areas entirely and then pay the working class fair wages.
As for defending the rural areas with force, that's the whole point of having a national military - it's not like we're going to forcibly conscript everyone just because they happen to live in the region.