It's funny you'd bring this up because I was just talking about this the other day. I've never used a pitch wheel as a controller, other than for pitch, and it might not be a very good idea, but I think it's worth trying. (It's possible on Digital Performer by using the pull-down menu "Reassign continuous data" on the MIDI track and then choose "from pitch bend" and "to Controller ##")
The reason it might be worth trying is because the pitch wheel, used as a dynamic controller, would work essentially the same way live wind, brass, and strings work. You put pressure on something to create a sound and get louder, and then you release pressure to get softer and end the sound. They're similar actions, but it's the difference between pushing a boulder up a hill and backing the bolder back down. Releasing pressure is a controlled return, and the controller curves look different than when creating pressure. There's a difference in the wind data (captured electronically) at the beginning of phrases versus the ends of phrases, and it's because the wind player is doing two different things: creating pressure and releasing pressure. When you're using a fader or a pedal, you're pretty much doing the same action, just in opposite directions.
The pitch wheel might be a better controller for dynamics than a fader or a pedal. Or it might sound like crap. Let us know!