One of my players is playing a Forest Gnome Artificer and is intending on being a bit of an inventor, comes up with crazy solutions on the fly, kind of character. But he just came up with an idea that sound a bit too crazy to be balanced.
In the previous session he set up a tripwire trap with a light crossbow, I let it happen, however he could not move or aim the crossbow, so it shot in a straight line (and missed as a result). But more importantly for him, it wouldn't automatically reload. So he decided to come up with a solution involving the forest gnomes ability Speak with Small Beast.
"What if I talk to a rabbit and convince it to run in a hamster wheel, and using a similar system to a train wheel to pull back the drawstring, set up a wooden magazine on top of the crossbow so an arrow falls into place and it resets for the next time the tripwire is triggered"
This to me sounds genius but also has a great potential for mis-use. What potential draw backs (pardon the pun) should I include with this invention? a "misfire" score? multiple tinker's checks? increased reload time? animal handling checks?