I skipped most of the early posts, so I might be repeating some.
I’ll resist fancy stuff and stick to some basics.
First, I’ll add another vote for a larger capacity still.
To limit variables, it might have be completely filled to work, and completely finished before any can be taken. On a side note, it would be useful to know any still’s status more precisely by examination (right click) rather than experiment.
Cave entrance hatch. Walkable, accessed by standing (skipping a turn) on top, both ways.
It would be relatively resource+stamina heavy, but can be installed from either side.
A hatch could also brace against caveins of adjacent tiles, while unsupported holes remain vulnerable.
Cave bracing with a wide area of effect, perhaps 5×5. Only effective when installed inside caves.
Option to clear data without starting a dummy game first.