I have no idea why people think elephants are linked to warm maps... They're linked to tropical ones; the temperature has little to do with it.
Looking in the object folder- elephants appear on any tropical forest and tropical shrublands.
Additionally, Elephants are not predatory animals. It doesn't matter if the map is calm; they'll still show up, though in smaller numbers.
If you just want a more difficult map to play on, try any of the good or evil maps. On good maps there are huge herds of unicorns- and unicorns are absolutely deadly (though they aren't useful in any way, as you can't tame or eat them... I think). On evil maps you might have one of many really deadly evil critters- Harpies, ogres, werewolves, etc. Either that or you have undead normal animals- these are far more aggressive and deadly than their living counterparts...
As for replaying sites that have been abandoned... It does happen sometimes that you can reselect an abandoned site for a new fortress... But I have no idea under what circumstances this works... I know I have a world with two abandoned fortresses, and I can select one of the sites for a new fortress, but not the other...
If you really want, you could reclaim, lock the doors to the old fortress and start a new one to the north/south...
Also, I can't understand this one-world mentality... My latest fortress is set in World 81, and my save folder is 1.5 gigs... Really, I should probably clean that up...