Some great POD's they could do which are touched on here would be incorporating the various mechanics with new cards into existing decks. Terrain cards for each extra deck....Highlands deck, Dungeon deck, city deck and dragon decks.
Lycanthrope cards into the various decks.
Burn/Fireproof cards to the decks.
Updated cards to replace some cards with wacky text or contradictory text that doesn't mesh well with a lot of various expansions that have since been released. This would be a great step towards streamlining the game and making it a complete game rather than mis-fitting puzzle pieces mashed together.
Maybe have some sort of fan vote for a cool POD expansion. You could use a lot of the expansions off of TalismanIsland as a base for these. There are some great ideas there, that a lot of people would like to see printed because they do not desire to take the time to make them on their own.
Frankly, I LOVE timescape. That is the only full expansion I have created off of the home brews. It is very good and works well for me. We even added some of our own cards to the deck that incorporated various mechanics into the deck.
Everyone seems to desire the Sea. This is one I would like to see but I don't want it replacing the Dragon tower. Currently we are cutting a second dragon board we copied and are making a tower with the spaces. We are making the tower so it has a dual purpose of holding the revealed or hidden ending card for all to see and making it so it holds cards. We have always put towers of cards in the middle of the board so this is an easy step. To make the tower more accessible we are putting it on a turntable so you can spin it to see the spaces without moving.