I'm really liking the sound of it now. Rip the audio and video into Womble. Replace all audio and video sections with DVD clips that match, and those that don't replace with ABC clips and upmixed audio.
But then again if it's 4x3 that means either the extra bits must be cropped to look 16x9 or the pan and scan DVD needs to be used. I don't particularly like either answer there. I suppose maybe 4-side black borders on the ABC clips would be ok, but that'd be a small picture.