You suggest that this will allow artisans to focus more on quality. If quality is important to consumers, they would be able to focus on it anyway and send along the extra cost to the buyers.

Subsidies always hurt those they’re meant to help by encouraging them to be less efficient, less competitive, and more wasteful. Also, they have tendency to create inequity in the system, with some people getting a lot more for less work than other people. If widespread enough, they can create dangerous inflation because you have an influx of income for some who have more buying power, while others suffer under their former incomes, trying to get by during rising costs. And if you think the average coffee farmer is the guy who will jump through the hoops and have the information to jump through the hoops to be part of a fair trade program, you’re kidding yourself. You’re probably helping some guy who was already doing pretty well to begin with, just like agricultural subsidies in the US end up helping corporate farms more than the family farms. And even then, do you think those profits are getting passed along to the pickers in the fields?

Also, you encourage people to move to a cash crop like coffee and away from other crops even more than they might otherwise. It’s the same effect that illicit drugs have on local agriculture.