Hey everyone! Turns out you can pick up player 2, and take them places. This seemed to obvious to not do.
I present: LEGO Taking a Hobbit to Isengard
Now, the hard numbers! This took about half an hour to actually do, with a significant detour when I got lost at Caradhras, which I've cut out. Turns out you can smash through the blockage from the back, but not the front, so I fast travelled behind it to smash the pass open, and continued my journey from there.
Also, notice after hopping off the boat, that there's a set of orange pole jumps. Those take you almost directly to Isengard, but my Orc can't go up the pole jumps, so we went the long way. At this point, I had no idea if it was even possible to get to Isengard, so I decided to push through and see if I could huck it round. Luckily, I could. This would have been a very different video if not.