I love to run campaign in the Nentir Vale, so anything related to it might interest me. The thing that I like the most with the Nentir Vale is the actual lack of information on the greater world, the complet history etc: it helps the point of light feel of the setting. So the thing I'd want is not new stuff that add 1000 new towns to the setting with the complet history of the region, but something that extend the few lore we already have: the Dawn War, the bickering gods and their primordial foes, the Living Gate etc.
Yesterday while looking at the map of the setting with a PotA campaign in mind, I realized the similarity in genre and tone between the Vale and Hyrule from N64 Ocarina of Time: a small dose of forest, lake, mountains, adventurers are rare heroes, the importance of the shadowfell and the feywild, the lack of major settlements etc. It gave me an urge to change my usual gritty/grimmdark tone I give to every game I play to a more pastoral/heart fantasy vibe.
I'd like a supplement that gives information on how to use the specific PoL setting as a Pastoral/Heart fantasy setting to balance the appocalyptic world of Darksun, the generic medieval fantasy of FR or the fantasy sci-fi of Spelljammer/Planescape.