So these guys definitely need to be a node. Maybe they set a trap, and then you have an outright confrontation? Trap ideas?
Falling stones is oh so form-fitting. Oh! and then you see them cackling maniacally from the cliffs above and rushing off ahead of you! While you have to clear the path/go-around! Only to face them again in a later scene!
If you want to use a falling-stone trap, the Titan's Goblet could make a good setting for their node. "The gnomes of Titan". Racing them to an objective at the top, maybe?
The weasel can climb and swim. How will the players get their chariot to the top? Maybe the choice is between means of conveyance and what they're willing to sacrifice to beat the weasel. Phrasing.
The outer paths at least would also need to worry about the gnomes interfering in addition to other hazards. Possibly not in a cave network, which could make it initially more attractive, but then there would be more dangerous hazards in there.