For the record, a solution exists at https://github.com/elygre/pldoc2/commit/38006267ab3c56abd20d68e049a1dc2c507c6b4c.
Variables in CREATE TYPE should not be sorted
Documentation for "create type" is not included
Variable named timestamp breaks parser
Btw, the following might actually be enough to make things work, though I'm not entirely...
OneJar thread context classloader handling does not work properly