Can a script launch a file picker? Or can a launcher script become a core/platform?

I have a game engine binary (usagi engine) and some games. A game can be launched with this command.

./usagi run ./games/notetris.usagi”

A script for every game would be annoying so I figured I must make a launcher app. But the only thing this app would do is pick a file and then substitute the path into the command shown above, so maybe it doesn’t need to be an app at all.

I’m new to muos development so I have two ideas but I don’t know how to do either of them, and would like advice on how to accomplish this in a way that benefits the most people. My ideas are these.

  1. Have a script that launches a built-in file picker (I don’t know if this exists) and then when a selected file path comes back, use it in the command shown above to launch the selected game.

  2. Get .usagi files to be treated like ROMs, but instead of the selected file path going to a script that launches retroarch or portmaster, it goes to my script which launches usagi.

and then fallback option 3 is using Love2D for a simple graphical file picker and launcher. But I want to know if that’s unnecessary.