Make gemmed blowpipes for lower levels, Sapphire, Emerald, Ruby, Diamond, and finally Dragonstone. No Onyx because it'd directly compete with Toxic Blowpipe, which isn't the purpose of this suggestion.
It would be crafting related, of course, and would take a combination of a matching level of logs along with the gem to make.
The items would give no extra benefit other than higher damage output and slightly increased range compared to 1-handing darts. None of the blowpipes would compete in damage output to the Toxic Blowpipe to make getting a TBP feel like a large upgrade.
This would make gems slightly more valuable, on top of making lower tier darts more valuable, without having any negative effects on the TPB, since it would still be a high tier choice for ranging at higher levels.