New subclasses will be
Isengard uruk - has increased stats of normal uruk
New abilities are
1.Call of isengard (starts from level 3 has 2 levels) - summon 3/4 squads of random uruk units for 30 seconds.
2.Sighn of White Hand - places white hand idol on the map that gives incresed stats)
About new lair system ... Surprise will be for you ))