> you could configure the syntax however you wanted. And sure, it would be persisted to disk in some canonical representation, maybe text, maybe a DB ... but you'd never need to worry about it, because all your tooling (VCS, diffs, refactoring tools, etc) would work with the AST, and you'd never need to worry about tabs or spaces ever again.

You are describing an entire industry of IDE Smell with an IDE monoculture.