Julia calls itself homoiconic, it uses Expr to model its AST and the parser returns it. There's even a show_expr method that prints it as an S-expression.

It just goes through great lengths to somehow have a textual representation that isn't s-expression based and then parse/print back and forth between the two.

Julia also has plenty of prescribed preferred data-structure, it has a standard Array with a Vector literal [1,2,3] which is heterogeneous and it has a standard Dict type as well.

So I'm seeing nothing that would be problematic if it had just gone with a Lisp syntax.