RE; IND-AMS, as hip as it may be, weighs in at #24 on the brookings institute report (2011) -14.3%, 5492 pax/yr and would be good for hardly any o&d and probably cannibalize our chances for LHR, FRA, ect.... due to it's proximity. I also don't know of any direct business ties.
In order according to the report;
London 30,732 pax/yr -4.6% over 2003
FRA 13,932 -17.9%
CDG 10,785 -11.7%
FCO 7,546 +49.3%
Manchester, UK 6,375 23.1%
Both the UK and Germany have other cities outside of their main airports with additional business / o&d ties that would make them the most logical choice ie. BA, DE as LH seems to be out of the picture. Not sure why DE was never mentioned publicly yet AMS was.
Interesting, the business ties to AMS I am aware of have to do with Lilly, ALSN, and Cummins, here are some more http://economicties.org/state/indiana/
although you are right there aren't as many...
One thing that is important to note is that (Global Air Volume:$106 million)Lilly's air suppliers are: Southwest(US), United (TPAC), and Delta(US/Europe)
(Global Air Volume: $308 million) Roche's are: American, British, Delta, Lufthansa, Swiss, United
So any carrier whether it is BA/DE/DL/e.t.c will want to have contracts with those two companies(which DL does) + plus contracts RR and Cummins(No idea what their biz travel situation is)
Therefore, DL is probably at an advantage over BA in terms of corporate contracts and considering they operate two main hubs in Europe, CDG and AMS are the most likely for TATL service.
In terms of O&D, CDG makes more sense than AMS, considering the aerospace industry in Indiana and other French businesses around Central Indiana. But, perhaps DL/KL are trying to beef up AMS, considering they just added MCO-AMS.
O&D wise UK/Ireland would make more sense: Delphi, RR, Lilly, Cummins, Salesforce MC, Allegion, Appirio, ALSN, e.t.c.
Also one reason why I think DE wasn't mentioned was because of the fact that it is a "leisure" airline, and the airport is looking more for a "business" type airline. Germany would have been great but in terms of LH there is hardly any UA FFs in IND, even though Evonik, ThyssenKrupp, Festool, e.t.c have large presences in Central Indiana.