Well, I think the problem with MSY is that you're surrounded by big hubs- IAH, ATL, MIA, etc. In this day with alliances it's become easier for the big airlines to simply feed passengers into those hubs, then have them connect onto their partner airline for continuing flights. I think this is the case with MSY. Airlines like Air France are probably interested in MSY, but have found it more cost efficient to simply slap their code on Delta out of ATL. Personally I think if someone tried serving MSY, it'd work, but who knows. I'd be willing to bet Boston service is not far in coming, and with UA expanding at LAX a second daily MSY-LAX isn't that far fetched of an idea. However UA is kinda low on aircraft right now with all these new flights being started so it could be a while before anything happens.
As far as Indianapolis goes, I'm not sure that's big enough of an international market to warrant any service. Again, it's easier for an airline to get their pax into IND simply by codesharing out of the surrounding airports like ORD.
Now, BA actually does hold rights to serve CMH. They actually recently renewed them. If BA were to ever start service to CMH, it'd be via PHL, according to their application. However I think BA is going to wait and see what happens with their alliance with AA and their seat cutting experiment before starting any new flights to the US. There's a bad case of over capacity on the North Atlantic, and that's really hurting the chances of places like CMH of getting non-stop service to Europe.