I'm familiar with the concept of wiring and similar methods of bending trunk and branches, but is it a viable option to either pot the tree at an angle or keep the entire pot at an angle? I'm assuming the tree will attempt to grow vertically in that scenario. If it's common for people to do that, is it a good way to create movement in a trunk that is perhaps too stiff to wire?
If you have a straight, thick trunk that can not be bent with wire, you will always have a straight trunk. Trunks, once they put down layers of hard wood wont bend to the light.
The best scenario with this is to either design a formal upright (not easy to do convincingly apparently) or chop the tree to a lower branch and try to do something with that.
Just be careful not to make a tree with 6 inches of straight trunk that suddenly curves into something else. It wont make for a convincing picture generally.
You create movement in younger trunks by wiring them when they are small enough to do so and let them grow out that way.