Burrows or candy wouldn't have solved it, methinks. I had steel, and forbade every bar except for steel, and he just sat in the forge, refusing to get the steel. Once I realized that he liked aluminum, I unforbade the aluminum bars and he immediately grabbed one. I doubt that burrows would have acted differently, nor would having candy available. If I didn't have any aluminum bars, I'm not sure if his aluminum preference would have mattered. If he still would have held out for aluminum, then aluminum is a very bad preference, since most forts never have it available at all, so a smith that insisted on it would go crazy a large percentage of the time, rather than just create a worthless artifact. But if he would have taken the steel if I didn't have any aluminum, then it's not all that bad.
But that's not really relevant. I agree that figuring out the weighting isn't the top priority at the moment. What I'm seeing is that a lot of the role valuation will be very dependent on the player and the situation. If you never use breastplates, then an armorer who likes breastplates doesn't matter, but if you use them then it does. I give all of my troops metal helms, even my archers who wear mostly leather. So a leathercrafter who likes helms isn't valuable to me. Others go with the default archer uniform and would benefit from a leatherworker who likes helms. Metalcrafters who like silver in a fort with no silver ores. Carpenters who like doors in a desert embark that doesn't have enough wood to be able to make wooden doors. Lots of situations where a normally good preference isn't worth anything.
I think the most important thing is to make it easy for people to customize the weightings for roles on the fly. Currently (I think) that means creating a new role, copied from a default role, and creating a new grid, copied from a default grid, and replacing the default role with the new one. I'm not sure if there's a better way to do it.
Keith