Usually the images I drop into Scrivener documents are much larger than required, which increases the file size and adds a tiny but noticeable lag to navigating to documents containing large images. In Apple Pages there is an option Reduce File Size, which (among other things) scales down image sizes in the entire document to only the size required by their layout size. I think something similar could be beneficial to Scrivener.
Rather than do this in an entire project, I’d imagine a “Resample image” checkbox could be added to the Edit Image dialogue that pops up when an image is double-clicked, basically mimicking the Adjust Size dialogue in Apple Preview.
So the user’s workflow would be to drop in an image, double-click it, adjust to the size, then check this Resample Image box before clicking OK, and this would then resample the inline image to reduce its size. (I guess perhaps a user could also resample an image to be larger too?)
This addition could reduce navigation lag when adding large images to documents, and reduce overall project sizes, making them more portable, easier to synchronise, and speeding up backups.