T.A, if I actually knew what I was talking about, I might be able to help fix it. Unfortunately, all I can do is guess.
For sound to match your movies, I suppose you could run the same demo twice--once with the earlier sound client to get the noises (at least, the ones that were in game then), then run it again with i23/i24 to get your updated graphics of maps, costumes parts, what-have-you. Slapping the sound from the first onto the graphics of the second--that's a thing now, isn't it?
Another workaround I was wondering about was if you could throw all the i24 piggs into the data folder for the earlier build with sound to have your cake and eat it to.