Lua is intended to have it's own subfolder where it will be able to save and load files freely, similar to the replays folder and ghost data. This will also involve allowing Lua to know the currently running mod name (in order to save a "Lua gamedata" file specific to each mod) and the currently running save slot (in order to have it's own singleplayer progression savedata), in addition to just being able to save and load arbitrary files (which may work cross-game with compatible scripts), but the details aren't hammered out yet.
It has also been attempted to tie in custom Lua data to savegames and gamedata directly, but there were concerns about inseparable file bloat potentially being able to render legitimate vanilla saves into uselessly giant blobs several megabytes of "data" large.
