Nice idea!
I haven’t read everything, but I noticed that you wrote that Shortcuts only accept one input. That is partially true. If you encode the &, shortcuts can take multiple arguments and parse them as a dictionary.
For example:
shortcuts://run-shortcut?name=Shortcut_Name&input=foo=bar%26one=two
The only downside is that you need to encode the ampersands… I don’t know if that helps anyway.