XQ.E13 - how to construct a node in a namespace with computed name?

Dear WG,

I know I'm writing a bit past the PER review period, but for the last
few days I've been deprived of Internet access - hope your internal
process still allows doing something meaningful with my input. Having
read the erratum XQ.E13 for XQuery 1.0 I'm wondering how I should
proceed in order to construct an element or attribute in a namespace
whose name is to result from an expression instead of being given
literally as a URI. Is this being made intentionally impossible? If
so, why? If not, what's the workaround and why should we be forced to
use it?