Wiki Creole in 2006 standardized many wiki engines on {{{ }}} code blocks. {{{#!python ...}}} for language or other extensions. All of OP's other points were al

Wiki Creole in 2006 standardized many wiki engines on {{{ }}} code blocks. {{{#!python ...}}} for language or other extensions. All of OP's other points were also solved, at least in the most common implementation. Unfortunately people forgot about this IMO huge improvement.