I was looking into migrating the shadow project from gnome-doc-utils to a pure gettext solution. But found multiple hurdles.

The first was the lack of dockbook.its and .loc files. The itstool project contains at least the first. The files do not seem to support man pages properly. But even after some minor corrections
this is mainly blocked by the lack of a merge mode (#52159), that attributes such as "class" get dropped, and that inline tags get quoted instead of injected as-is.

Attached a tarball of a test case, showing some of the problems.

(Ideally DocBook 4 and 5 would be supported, itstool contains support for that and few other similar formats.)