I really wonder what Ike's FS is.....I never played POR(or ANY FE game for that matter :P) so I wouldnt have any idea....
I haven't played any FE games either, but according to wikipedia, the Fire Emblem is teh main characters object of desire. So maybe it would have something to do with Ike's Fire Emblem.
Fire Emblem games are TBS games and every character really only has a normal attack animation and a critical one... Nintendo has a lot of freedom in their character development. Also the characters can be upgraded to a better class after a while. Maybe Ike will become a Lord Knight for a while when using his FS? (I didn't play PoR too much, it was boring. ><. I played the other FE games released in America.) Basically Nintendo can do whatever they want for Ike's moveset and FS.
i think like the whole stage goes up in flames or somethin...(i havent played any FS game either so i wouldnt know :P)