Not sure if such transpilation would have a perf hit though, I hope somebody responds who knows about it more.
I don't deny that syntax matters itself too but there are some ideas of janet like sandboxing and other features which seem to me to be worth implementing in other languages too.
Personally, I would be really interested in a language like lua/wren which can transpile to Janet too.
I guess you don't like Lisp's syntax. I didn't either until I realized the key insight: when you're writing Lisp, you're basically writing an AST. Which is why it's so easy to manipulate your code. Want a new feature the language doesn't have, such as the pattern-matching they added to C# a few versions back? You can add it yourself; you don't need to wait for a language committee to implement it years after you needed it. That's all that macros are: functions that take AST and return AST, which is then executed.
And once I realized that Lisp's syntax was basically an AST, I no longer saw the parentheses. Now I just see blonde, brunette, redhead... Oops. Sorry. Wrong reference.