Does renpy even support patching? I've never seen a patch for a renpy game, afaik all the content is packed into bulk directories.
Depends on how files are stored. Some developers pack all images/text into few files like chapter1,chater2,images and others create 1 file per room/location and store images in one folder
freely(by that i mean that you can get in folder and check every one of them yourself without playing with unpackers).
if its case 1 then you would need to download everything anyway as it's stored in few big files>small update is
impossible.
in case 2 usually(most of time, depends on how big update does devs make) only few renpy .rpa/rpy files gets added/updated(files where text and dialogue + and some pictures are added to folder).>small update is
possible.
Biggest hurdle in case 2 would be making notes what exactly was added compared to previous version as missing file(either rpa with text or pictures) would create errors, most of time game breakings ones(well maybe not pictures, but you get what I mean).
That's why you
almost never see games get
small patches until those are incest/loli/trans type (images included or not).