I don't get how GXP could be finalized in a single volume, especially with the the rather tedious pace of novel 17 (getting rich farming magic dirt-pigs, making friends with little kids you'll never see again, visiting the library, slowly learning magic, super sloppy Jovia intro [the fault of the robo-translation]).
So, he'll have to join an adventuring group, master magic, join the army as a scrub, figure out what's up with the new AI girl stuck in his head/skin (never hinted at in the OVA or PW), marry Airen and Jovia, have Kiriko join the adventuring group, finally leave the planet... win a war, marry 8 more girls.