I think the best goal keeper is the one that belongs to the Al-Bhed Psychs (Nimrook?). There's a chance that they'll drop him once his contract expires, so if you snatch him up straight away you'll have an amazing goalie. Also Ropp, who works at the Rin's Agency on the Mihen Hiroad is an excellent goal defence. He comes with high Hp etc and has Venom Tackle 2 or 3 already learnt.

Also also Blappa, one of the Al-Bhed Psychs forwards is one of the best players too. Combine all of them with Brother and you've got almost an entire team of Al-Bhed.