After having spent a lot of time on this, finally here's the procedure that enables 6 new GPON-related options that might help some people to get O5 status in XX530v V1.

XX530v: How to access hidden GPON Settings

Please note I've created the feature request below, so you're encouraged to vote as well, because I can't guarantee this procedure will make XX530v V1 compatible with all ISPs:

XX530v - Allow changing VENDOR ID, SOFTWARE VERSION and other parameters for great OLT compatibility

Enjoy.