The GWSDL inheritence mechanism seems to be limited to one level when RPs are
involved. I tried inheriting a WSDL with RPs that already inherited a WSDL with
RPs and it complained that it couldn't resolve the second WSDL's RPs. The
operations were inherited just fine.

The workaround is to inherit the second WSDL directly and extend from it
explicitly even though it should be already inherited indirectly from the first
WSDL. It works, but it creates duplicate import statements which doesn't look
very nice.