I've finally printed out the outer cover to see if there's any obvious issues, but more to make sure it's printable in the first place.
I've also looked a bit closer at the hotend and noticed that 2 of the 4 heatbreaks actually leaked a small amount of material. Considering I've only put in a small amount of material, I'm going to have to some cleaning and tightening. At the same time, I'm actually not sure on a suitable strategy for actually going about sealing that still allows the hotend to print at 250C without offgassing concerns.
I think a good place to start is getting heatbreaks that can be tightened using a wrench. Unlike traditional hotends where the nozzle is tightened to provide the seal, the tightening has to come from the heatbrake with this kind of design. The E3D Cyclops seems to adopt 2 flattened parts of the thread to allow for this:
It's likely so that the torque of tightening the heatbreak doesn't risk shearing the thin heatbreak section. One of the issues I'm encountering in my mental simulations is that there's a lot of stuff around the heatbreaks (such as other heatbrakes or thermistor wires) that would seem to make a wrench-tightened solution difficult.