> bracket pairs like (), [], {} are way too precious, imo, to squander on something like blocks

I disagree. Besides (), [], {}, and <>, there's plenty of other paired punctuation available in Unicode, such as...

⦃⦄⦅⦆⦇⦈⦉⦊⦋⦌⦍⦎⦏⦐⦑⦒⦓⦔⦖⦕⦗⦘⧘⧙⧚⧛⧼⧽〈〉《》「」『』【】〔〕〖〗〘〙〚〛❨❩❪❫❬❭❮❯❰❱❲❳❴❵⟦⟧⟨⟩⟪⟫