Since, as I've pointed out, the editor can handle the parens for you completely and unabiguously, even without any special commands, you could simply turn-off, parens that exist in addition to indentation, make them invisible.
If you then additionally make the editor display the opening parenthesis as a colon then, voila, you have the visually pleasing colon syntax.
In such a mode you'd always have to be indentation perfect, but just as with colon syntax, you can simply switch to a more traditional editing mode.
