Well, it's probably been done by someone, maybe more than that, but they're not done very often, whether because leaves don't reduce well (I'm just guessing here), or branches are hard to shape (ditto), I don't know the tree except by name, so you could try Googling P... bonsai and see what comes up. I do know that the actual "Foxglove" plant is Digitatata (or similar) and is used to make digitalis the heart medication, plus the plant is very toxic! So maybe just use the Paulownia name so as not to confuse people :-). Oh, and don't try to grow it indoors because it will need months of cold dormancy like any other N. American native, and will definitely not survive inside for any length of time.