As can be seen in the photo of post #41, modding an ordinary driver into a DML exciter, the difficulty is in connecting the VC to the panel.
The VC of a cone driver is deep under the frame, one has to extend it long enough to be higher than the front surface of frame. So it'd be better if the frame is cut to free up the VC.
And then, to mount it on the panel, it needs additional external support to float above the panel. Some soft gasket on the existing frame might work (if not being cut), but not ideal. Those are going to be damping points and too close to the VC.
Eventually, I think it's not very cost effective to do such mods. It can be done and it'll make some sound, of course. But for better performance, proper exciters are worthy. And, actually they are cheap enough.