Re 3)a) - closing all inner is absolute nonsense, but it would make sense to use that as a further safeguard to prevent the case you mismatch braces in one place and accidentally "fix" it in another. I think it would be nice to be able to say "this is supposed to be the closing brace of matching that particular opening one, scream at me if it ain't". I don't think the "reversed label" syntax is possible without breaking a lot of stuff and the label syntax to mark the opening brace doesn't work well if you are not crazy enough to reserve a whole like just to the opening brace, but something like

if (whatever) {
  ... blah blah blah
  if (something) { ###FOOBAR
    ... a complicated code with plenty of braces
  } ###/FOOBAR

} else {
  ... some more code
}
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could actually be helpful in complex code in case you accidentally type one too many/few closing braces within that marked block.

You'd still have to have the right number and nesting of braces, but you'd have one more check in place should you decide to ask for it.