1:
So this is the original game "as is" + an expansion option for the new underground area.
Or is this the original game with the expansions built in (new abilities etc.) making it a different game from what I have now?
2:
New enemies? I don't want palette swaps (Chimera - Gore Chimera), (Wolf - Hellhoud).
1. It sounds like most of the expansion stuff aside from the new abilities and augments won't tie into the main story? Sounds kind of like a Shivering isles thing where majority of the expansion will take place away from Gransys on that Isle (lol) and when you're done you return to Gransys as if nothing has happened...maybe. So yeah, it's the original game with new abilities and augments and additional area not on Gransys.
2. I saw some new enemies in the trailer, or at the very least new bosses and a few palette swaps like a zombie dragon and a red gargoyle I think. Also saw giant flaming lizards but they could just be more saurians.