It turns out that what I thought was so clever yesterday, was done some time ago by folks at DePauw:
MAGIS, an inventory of regional survey projects in the greater Mediterranean region.
As of today, they have 288 survey projects in their spatially-searchable database. The interface is a bit clunky though, and relies on popups, which my browser consistently shuts down, despite me telling it not too. Platial and my BiblioCartography also have the advantage of allowing others to embed the maps in their own applications. If I get around to it, I might incorporate the MAGIS inventory.