I might remove plastic, actually.
The only reason I put it in was due to a quirk, specifically that DF machinery requires logs, but gnomes are supposed to be nature-friendly and would prefer not to cut down trees if they could help it (they aren't quite as tree-huggy as elves, but still). I thought of giving them the ability to carve logs out of stone or metal, but the carpenter can actually carve any logs regardless of what they are made of (and presumably the wood burner works the same way), so this wouldn't make sense. So I tried to think of something artificial that was soft-ish and cuttable like wood, and I came up with plastic.
But plastic is kind of synonymous with 'not nature-friendly', so it doesn't really suit the gnomes all that well. Also, I might remove advanced chemistry from gnome technology altogether, giving them a sort of 'schizo-tech' image (21st+ century physics, early medieval chemistry).
Also, the ability to produce unlimited wooden logs is just the sort of thing they could obtain from the elves.