When ssm is used as a filter, it doesn't order its arguments correctly (namely {{ parameter | ssm options}} becomes {{ ssm options parameter }} instead of {{ ssm parameter options}}.
This fails /w error calling ssm: Invalid option: parameter. Valid options: [required prefix region].
Chaining filters is a nice templating feature that we've used for other things (quoting, manipulation) and it would be nice to be able to use it consistently.