To complete the Extended Superman Trilogy or whatever you want to call it, a collection along these lines would be excellent if somone could make it possible:
Superman: The Movie - KCOP TV Version
Bonus Material (Trailers/The Making of Superman: The Movie)
Superman III - Extended TV Version
Bonus Material (Trailers/The Making of Superman III)
Sadly I don't think there's anything to expand on Superman IV as of yet. The popular stance is that all the lost footage was destroyed, but I've also heard evidence to the contrary. We'll just have to hope for an anthology set like Batman's to be released next year after Superman Returns. The odds are low for a restoration of IV, but it would be an absolute crime not to do a special edition for II. It's exactly the kind of movie the DVD format was made for.