I think that this is a cool idea that will work. Although New York is a great O&D location, it didn't necesarily serve UA well since they didn't have so many flights to and from JFK.
IAD works well because it is also a major hub for traffic to Europe on UA. The connections are very feasable from AMS, CDG, BRU, LHR, FRA, MUC, DUS and MXP, plus the codeshares to CPH, VIE and MAN.
Good thinking in my opinion. Didn't varig used to fly to IAD via ATL?