I've heard of Obsidian, but never used it. I am afraid I'm not familiar enough with the whole idea to create plugins for it, I don't even know what integrating would mean in this case.
Obsidian can use HTML so it might not be that difficult to do.
What would be even easier for you is if we could download the files in markdown format (instead of the format we download then now in). If you did somehow get it set so we could download in the markdown format it would fall on our end to integrate it how we wanted into Obsidian.