Just a quick update: The gantry is almost fully-enclosed with 0.125" laser-cut plywood. This video shows off some of the finer details in action.
At this point, I'd almost call it done, except my laser diode has stopped cutting through as consistently as it did on its first cut and it's now struggling to cut through cereal boxes unless I bring the feed down to a sluggish ~10mm-per-minute. I suspect dust on the lense is to blame, and I'll need to add ventilation shortly. I may also need to adjust the focus of the laser as the first cuts were done on a piece of cardboard that was curved upwards about 0.125" closer to the laser diode than the cuts shown here.