Hmmm - re. the theatrical DTS, three possibilities here;

1 - Waterworld had 5.1 DTS theatrically (as suggested in the other thread by the guy who actually did the mix) and the 4.0 information is incorrect

2 - Shawn's 4.0 rip had to be remapped within 5.1 because the decoder dictated it, but it still only consists of four discrete channels of information - have you checked that the LFE has content and the surrounds are split?

3 - The encoder actually processed the channels to derive a full 5.1 spread (including frequency filtering for the LFE). Obviously this is an undesirable outcome if we're after preservation

Anyway, I'm sure Shawn can quickly clear this up. Taking a long view on the choice of tracks, I'd suggest the following:

Theatrical DTS
Theatrical Dolby SR stereo (as represented by the LD PCM)
Blu-ray DTS-HD MA (a modern home theatre mix in lossless format)

Plus any foreign language dubs, subtitles that people request? That should cover all the generations of this soundtrack, unless folks know something else about intermediate versions (e.g. laserdisc and DVD DTS).