I'm not sure how cold winter gets in your friend's area... but if the water temp will dip under the mid/low 70's, i wouldnt reccomend any tropical cichlids, or tropical aquarium fish in general for that matter.
IF, however, the temp will stay in the 70s, there are quite a few options.
Green terrors, red devils, oscars, pbass, texas, and midas could all probably be kept in the pond if it had a stable ecosystem and proper spawning grounds.
Convicts would be able to live there too, but wouldn't be good fishing stock because of their small size.
as far as other oddballs go, I'm hesitant to suggest anything because I'm not sure how the ecosystem would work out. One thing to be sure of is whats in the pond already. ther needs to be a healthy population of small fish and plants to provide food for your friends stock.