Don’t have much to add to this. Open folder as an Obsidian vault from terminal / command line / CLI seems to me like the most promising solution for your problem and many other problems. If the Obsidian CLI gets this functionality creating this context menu option would be a trivial command instead of a unstable script like you propose:
// NOT WORKING
obsidian vault C:\path\to\vault
start obsidian://open?path=C:\path\to\vault
Just swap out the path to a relative path and it works.