With indentation-based languages the bad coding style we are talking about is putting multiple statements on a line or unindenting a block …& never has that been something I wanted to do. I would rather this aspect be enforced at the language for readability where there is still room in all other aspects to try out other styles.

Why haven't custom parsers become more of a thing? All the compiler or interpreter really needs is a valid parse tree. You could even have some kind of special command or directive to switch styles, if a section would be really ugly otherwise.