Advanced Mac Substitute stores documents and preference files in sandboxed host directories.

For example, check out the MacPaint demo:

https://www.v68k.org/advanced-mac-substitute/demo/MacPaint-A...

If you were to double-click the Hello document in macOS' Finder, it would launch and open in MacPaint.app.

This is exactly the sort of project that can serve as the basis for such a system.