I know you're joking but uh yes I like this for all the glorious yet hot silliness it would be.

Prussia and Austria in bed one night and Prussia trolling, asking about Spain's ass, putting it out there that it might not be real. And Austria looks at him like he's nuts, of course it's real, idiot, I was married to it for hundreds of years. And then stupid bickering until they agree to invite Spain to their bed and ~find out~