This is a great topic, @tom!
At the risk of sounding like a broken record, I would love to see some Deutscher Sekt as well as Austrian Sekt on the list of sparkling wines (Dr. Loosen, Weingut Aldinger, Weingut Steininger, Johanneshof Reinisch etc.). There are some really good ones out there! I would also love to see a few more examples of Austrian wines (this has been discussed on another thread too) other than Gruner/Zweigelt. There are some fine wines made from Zierfandler and Rotgipfler in the Thermenregion, the top ones of which are an excellent alternative to white Burgundy, at (often) half the price, as well as Pinot Noir from the likes of Birgit Braunstein (she makes lovely ones in Burgenland) and Stift Klosterneuburg.
And continuing on the theme of more esoteric wines - some Cornalin from Switzerland (TWS used to stock the one from Domaine des Muses, but it’s no longer available), or from Valle d’Aosta would be nice to see (Grosjean, for example), as well as some good quality Swiss Chasselas.
Perhaps it’s a bit niche, I don’t know - maybe even difficult to source, but we did use to have some Swiss wine, so a comeback would be nice