Physically Accurate 2-Part Architecture
Scale
The line lowering the canister is an industrial-grade umbilical. It provides the structural strength to lower the payload, contains hoses that pump the bio-slurry down, and acts as the vertical track for a pressurized astronaut elevator pod.
Notice the canister at the bottom. It doesn't stretch or bend; it anchors in place to become the primary airlock. The side hatch opens, and the habitat balloons out of it, flaring under pressure until it locks against the 20m wide cave walls.