Talked today about making Rust macro token streams compatible with arbitrary DSLs, and think there's a plausible way forward by using raw strings. A downside is that depending on how it's structured it might feel odd. The upside is that those could be solved with syntactic sugar
Take: for a language to compete with JS's web (app) story, they must match the convenience of embedding DSLs inline. If a language can also solve the pre-processor complexity JS has, that would make a compelling advantage.