Add support for calculating the header value from Groovy (or others?) script like SpEL.
<header name="logId" ref="logRequestResponseAction" method="log"/>
I do not think it should be full support for nested beans, as shown by Oleg, because in this case the header value will be calculated only once - when the application is starting.
And it will look like StaticHeaderValueMessageProcessor strategy.
In other words, it would be redundant.