Note that in Drafts 24 (released today), the Mac version has support for locally hosting images in a Previews folder for previewing purposes. It also won’t work with Marked2, but including a pre-processor script could address that shortcoming.
The Previews folder utilisation doesn’t look to be available on iPhone/iPad (yet?), but the exploded Markdown preview approach does still allow you to host locally on any of the platforms (excluding Apple Watch of course).
Edit: I was mistaken, the new Previews folder support is cross platform.