You can happily mess around with camera views while looking at a dialog. No different to when you aren't in a dialog.
You can't resize the camera as such, but what you can do is have a full-screen dialog with a little hole (think of a stencil) in it to make it look as the camera is small.
(You do know that there are is least one full implementation of a
UAV released, including models? Just telling you in case you weren't aware of that).