You are correct about the FRA route- a slip on my part. The slots that TWA received at Frankfurt made a long (7 hours or so, if I remember correctly) turn time at FRA. Perhaps if AA decides to fly this route, they can swap with one of AA's existing slot times to have the turns make some more economic sense.

If TWA thought they could make STL-FRA work, there's probably a good chance that AA could as well.

STL-NRT would be an interesting option as well. JFK-CAI-RUH has done very well for TW in the past- apparently the CAI-RUH leg by itself pays for the entire trip.

STL's international facilities, in terms of sterile boarding areas and customs leave a bit to be desired. There was talk of the city relocating the international gates from the current location on the C concourse to the end of the D concourse at STL, close to WN's East Terminal.