There is a sawmill mod around, that basically turns a log into a number of generic blocks that have a wooden color.
Although, I have thought of taking the idea and expanding it, so you could maybe cut the logs into lumber, or something, and still make furniture out of it. It just kind of bugs me that it takes an ENTIRE tree to make a single, lousy bed? However, I'm not sure if this would work or not - or at least, not without making custom reactions or something.
Too make furniture, it would have to be a log, and the main problem people have with that is that using logs to make more logs is extremely problematic. However, I think you could solve the problem by duplicating the wood template, adding a reaction class to one of them, and then adding a second type of wood to every tree that doesn't have the reaction class. If you do that, I'm pretty sure you could create a reaction that takes a log of wood with the reaction class and creates, say, 3 logs of the processed variation of that tree.
I'm not 100% sure this would work. I did something similar when experimenting with paint, and while I never got an error report from the reaction during worldgen, I also never made it the testing phase. Mostly because I couldn't get my dwarves to actually create the paint itself.
Edit: Derp, looks like that's what you did huh? But you don't need to make custom trees, I think. You could mess with the template files, or just straight add it to each tree, since you would still have to add something to each one either way. Or maybe I can just shut up and actually read everything.