using expressions with append-string-transformer

Apparently, expressions cannot be used in the append-string-transformer message.

e.g.

<append-string-transformer name = "Foo" message = "Neither #[header:bar] nor #[header:bar2] work as expected." />

Of course, the work around is to chain several different transformers together, but it would be a lot cleaner and easier to just be able to use expressions in the append-string-transformer.

Is this a reasonable jira new enhancement?

Steve