Say I want to purchase a LONE4 from AA from a country where AA does not have ticketing offices, like Romania. I am considering buying it from BA with some random routing, and then having AA reissue it with the routing I want.

I would make the exchange before starting travel and not make any changes to the first international leg. I assume I can even originally buy a LONE3. Can I do the reissue in the US without having to pay the US price? Would AA simply calculate the new price (with low taxes) for the LONE4 and charge me the difference between that price and the LONE3 price (with high taxes) that I paid to BA? And there should be no 125.00 fee because I'm making the reroute prior to departure.

Am I correct in all of this? Has anyone done something similar?