Helsinki-Vantaa! It's uncrowded and a third runway is under construction, so capacity wouldn't be a problem. It was just voted the best overall airport in an IATA survey for 1998 (was 2nd worldwide, 1st in Europe in 1997), and the categories it was lacking in were the number of connections, especially intercontinental ones. So if these were better, maybe after becoming a hub for another airline besides Finnair, then HEL would be perfect, no?
Anyway, the location isn't excellent Europe-wise, granted, but it sits right in the middle of North America and Asia, and now thet there's this dominating airline for those routes competition wouldn't hurt.