For what it's worth, I'd really like to build a Second Brain, Obsidian, Digital Garden, Zettelkasten plugin, at least for myself. We have the infra to make it possible as a plugin, and you can probably hack the docs plugin to add [[keyword]] as a link to a doc tag page in the meantime (using a custom remark plugin)
Images can be co-localized with the content, although it increases the size of your Git repo over time