put optional step in different namespace

if we assume that the standard library, as defined with a
p:pipeline-library element is defined with a default namespace
attribute e.g.

namespace="http://www.w3.org/ns/xproc"

In the case for optional steps, is there not value in placing these in
a separate  pipeline-library definition with a different namespace
from the outset?

namespace="http://www.w3.org/ns/xproc-opt"

Jim Fuller