Right now it makes more sense to buy someone who specifically produces a resource because the multiplier means they produce it more effectively than you would by having a few improvements to cover just your needs.
By removing the multiplier, you could argue there would be more incentive to just have X number of farms per city to cover your needs rather than buy from someone who produces food in mass and more effectively. Even if it means just partially covering their needs, people may just fill any extra slots with farms over anything else as there's no reason not to -- since you aren't missing out on a multiplier.
If that ends up being the case and more people slot in a few farms for their builds, it will negate the effects of extra consumption / lack of a multiplier. The only leg up a dedicated food producer would have in this case is how much land they have.