Your approach sounds quite workable...but don't go with the "I'm quitting" thing for the purchased account, rather think about just not giving any specific reason, or if you do, of "changing focus"? With an account the age of yours, it should be totally doable, but don't have the purchased account go into an "I'm quitting" type of thing, and you don't even have to have it as an up-for-grabs thing with apps through boards: rather you can establish some sort of relationship via Neomail and conduct a trade without any board involvement...it's no one's business how you managed to make the trade, and it need not be public. Avoiding the boards as much as possible is VERY preferred.
Thanks for your input!!