It can be done fairly easily. It wouldn't be on my list, though.
Care to elaborate on this statement? While I get your ability to build nice appearing MDF kick panel enclosures, I don't have the equipment or desire to acquire the tools needed for visually nice pieces. The OP's question about the Dixie Restorations 'speaker' door panel alternative is what I've been wondering about as well or if some 4x10's (or similar size) couldn't be incorporated behind the carpeted section of the factory door panels for an 'unseen' improvement. Not trying to win any sort of competitions... Just want better sound from a basic set-up (stereo; 4 speakers [2xF; 2xR]; amp; small sub [8-10"] ).