we definitely need to give Gawain something to do next turn. He'll be 20, and he has better stats than us in nearly everything!
I'd avoid giving him the "trial year of rulership" right now, as we're probably VERY close to a new war, but if all goes as expected I think we could abdicate and give him the throne right after the next war with Maretonia, and maybe have Garrick take the role of advisor or ambassador if we want him to still do something.
Now, what could Gawain do in the meanwhile? well, we have more than a few options.
1) We could have him join one of the knight orders, possibly ask Hardbeak to take him as his squire. With his 19 martial it shouldn't take too long to rise through the ranks and become a knight, maybe even an elite knight after the next war.
2)We could have him be an ambassador to any of our allies. Neighpon, Canterbury, Yakyakistan, or even the minotaurs or dogs. with 19 Diplomacy he should do a great job, and he could make some usefull contacts for the future
3)We could have him try to manage a business, a fiefdom or a whole province/state (gryphonia, aquileia, or maybe the new province, Kestrella i think it was named?)
4)We could send him to study at the Crystal University, or work under Ravenburg, but they're not really his strong points (learning 12 and Intrigue 13)
5)We could combine one or more of these options. Example: we make him Hardbeak squire for 1 or 2 years, Once Hardbeak thinks he's ready we send them both to Canterbury as both ambassadors AND help against the local monsters AND to help them improve their army for the coming conflict with Maretonia (also to thank them for the magical advisors they sent).
If they do a good job we have a reason/excuse to give Gawain the title of Elite Knight, and he gains both martial and diplomatic experience plus some familiarity with the way of living of the Canterburians, which might give him some insight into what kind of trading goods they might be especially interested in.
..Actually I really like option 5 (basically 1+2 combined). What do you all think about it? Let's say 2 or 3 years of experience under Hardbeak, and 2 or 3 more years of experience as ambassador/military advisor/hunter of monsters in Canterbury, then he's back home and we either give him the throne or let him rule Kestrella or one of the other provinces until we actually decide to abdicate (assuming, of course, that Garrick doesn't die before)