About that sampling rate stuff, is that really a problem (SurCode seems to be able to create 48kHz-sampled DTS CDs)? We could just replace it's substream with a regular 16/44 WAV substream. All we need to do is get the DVD to recognize it as a CDDA and play it, the DTS decoder does the rest.
Now, back to the main question (ignoring the sampling rate issue, let's assume it's 44.1). There's a program called DTS Parser that turns a DTS-encoded WAV file into a regular DTS file, by stripping the WAV substream and recreating the DTS substream. What I want is exactly the opposite: a program that strips the DTS substream and replaces it with a WAV substream. Theoretically, it's possible to do it with a hex editor and the specs of both DTS and WAV formats. But, well, I don't have patience for that.