first you need to own the 51% of that airline. The LAN-TAM merge is still subject to approval. LAN does not have enough planes to take over TAM Long range operations. And does not have any planes on order that will allow to take over TAM ops. TAM has more than 20 Long Haul planes and lots of orders. They can order planes but it takes time to receive those planes. And yes, to fly PT aircraft you need to be a citizen in Brazil. You can fly short term contracts. Argentina is also a country were you need to be citizen to fly LV aircraft. You can fly short term contracts as a foreign pilot while you train local pilots. But not as a career. In Chile and Peru you can fly as an expat. No problem at all. Laws allow this to happen. Panama Also. I dont know in Colombia if you can.
Chile has some 5th right on Brazil routes but the Brazilian government will not allow this to happen. A Chilean company overtaking Long Haul operations of TAM airlines, the main Brazilian company today, with foreign crews flying for 2 cents while local Brazilian crews lost their JOB????? Yeah, right. That's why Unions exists. Sorry guys. Sit back, relax and enjoy your flight.