Unless I'm gravely misunderstand this feature currently, it won't help that use case as the variable assignment only supports string literals, env cars, or exis

Unless I'm gravely misunderstand this feature currently, it won't help that use case as the variable assignment only supports string literals, env cars, or existing files which wouldn't help your range request for the remote file It would be a natural extension to treat the @ syntax as a uri (because, come on, it's curl!) if it contains a ":" but even that gets hairy because the next layer of indirection would be --variable-with-curlrc to allow setting the enormous number of parameters one would want when chasing the interior uri