To be fair it's true that he's wasted here. Aside from the incompetent top brass of the kingdom posing more problems than the freaking actual enemy, the princess isn't really a wise queen or something. She has charisma but she's basically a figurehead for now and so the kingdom would in fact benefit under proper leadership - not to mention, by being an invader shandris would be able to clean out the nobles with 'justified reason.'