On the matter of not being able to use use plants and wood on embark, I've discovered that it's the indoor plants and wood only (i.e. plump helmets, tower caps, etc.). I'm looking into it, but if I include both the indoor and outdoor farming tags I can get outdoor crops and wood, and if I include only the outdoor farming tag I can get outdoor plants and wood. I'm not mislabeling the tag (through misspelling or otherwise) so I don't know what the problem is. This actually is an issue for me, as I prefer my gnomes live underground, and growing only above ground crops conflicts with fluff (which I value). I intend to force all my gnomes underground and see if that fixes the problem (I have them able to be underground and above ground currently, with more weight placed on underground settlements). What's odd is that Seth's gnomes can farm underground and my gnomes used his as a template, if anyone knows any other tags that can influence farming, please let me know, I may have changed one.
Seth, to make your gnomes gather plants from above ground, simply add the [OUTDOOR_FARMING] tag.
Working on plants is a great idea, I'll start modding up some gnomish alcohols from new underground plants once I get the farming issue sorted.
Edit:
Eureka! The problem of not being able to take underground plants and wood on embark appears to be due to specifying the starting biome to be mountain and some other. Therefore if you list two starting biomes, one of which is mountain, any underground farming won't work and your gnomes simply won't farm. So, if you want underground plants, either force the gnomes to start in the mountains only, or make sure they don't start there. Shintaro, if this doesn't solve your problem directly, try changing your starting biome combinations, there may be some other combinations that break the indoor farming tag.