How about this for thinking outside the box--
Once US is part of the Star Alliance, feed Lufthansa's large FRA hub from a few medium-sized airports at which US has a significant presence (in addition to service from PHL, PIT and CLT). I'm thinking possibly BDL-FRA and IND-FRA 3 or 4 times weekly each in the summer and maybe a similar split with MCO-FRA and TPA-FRA in the winter. The first 2 markets have no scheduled nonstops to Europe, and even the Florida markets have very little other than to the U.K.
Of course, this assumes that there is an extra 767 or 330 sitting around with nothing to do (at least internationally). But in addition to new nonstops to FRA, it would offer passengers in these cities single-connection service to numerous destinations throughout Europe, Africa, the Middle East, and even parts of Asia. And it has the potential to attract a loyal following at cities that have few, if any, other options for nonstop flights to Europe.