Apparently a number of (what appear to be) cave entrances on the moon have been identified. There is a long list of technical advantages to setting up a base in a cave, as opposed to surface modules. However, all the US proposals for a moon base seem to call for surface modules. One after the other, after the other.
Looking for more information, I saw an article, Russia Eyes Caves on Moon for Setting Up a Lunar Base. But a more accurate headline would probably be Boris Kryuchkov thinks that moon cave discoveries will influence moon base plans. The article doesn't give indication that the Russian space agency is looking into it (with the possible exception of the title, as often happens with headlines).
I want to ask: has any space agency done a study of a lunar outpost using in-place cave walls?
The task would still involve taking inflatable modules that would expand to fill the space, and these would still have to be extremely strong. Even if it's located in a long "lava tube", the ends still need to be sealed and rated to full atmosphere pressure. If it's not deep enough, then the walls can't resist the pressure in the first place. However, one pictures is said to indicate a depth of 100 m, and the surrounding soil pressure would exceed a full atmosphere below 60 m (1/6th gravity x density x height). That means that (depending on the cave) you could rely on the rock's strength. But maybe redundancy would rule that out.
I haven't mentioned yet, the air delivery systems would be different. Maybe a chemical Oxygen generator would be more mass-efficient than a pressure tank? There are so many things that would affect the assumptions for the mission funding and planning, I couldn't even begin to list them.
Are NASA plans just outdated because our knowledge of the moon has improved? To be more straightforward, has there been any study by a space agency that attempts the quantify the huge differences in mission parameters? Or is this idea just too far out there, or too new for something like that to exist?