How much easier would it really be to build resource workshops instead of furnaces? You'll need the same number of buildings either way, for gathering of resources to keep up with production.
I like being able to alternate gathering and use of resources at my furnaces. Sure, it slows the production rate at a given furnace, but it easily guarantees a stable resource supply. If things aren't being produced fast enough for my taste, I can always add more furnaces to keep my potters and glassmakers busy. I'm opposed to removing the resource gathering orders from the furnaces, though I have no objection to adding an additional workshop devoted to gathering resources.
Easier? Much easier at the start. Dunno about you but I tend to get a lot of wood cut before I even try cutting into the first stone layer.
Plus, unless people really want it used as a storage depot building, no dwarf will be working at it so it could be a 1x1 walkable building, with no material cost even. 9 of these could take as much space as a single furnace, without blocking a single tile.
It's really a trade off, if the collection jobs are in a separate building then manager jobs for collecting materials won't clog production buildings, and production tasks won't go to the wrong buildings (like making 600 clay bricks going to your non-magma kiln). Workshop (P)rofiles can really screw with your production too if you don't micromanage it all.
The best solution would involve this plus the ability to turn on/off manager control of a workshop's tasks. Turn off clay collection on your magma kilns and all manager jobs on your master potter's kiln (so he's free to keep making/glazing statues while your trainees work on the bricks), build a couple resource workshops, then queue up 600 clay bricks and 600 collect clay tasks.