Hi there.
SFAIK,
between "demuxing all the individual channels"
and "merging them back together",
one cannot avoid re-encoding, unfortunately.
In theory at least, it should be possible to convert (losslessly) a multichannel DTS into a set of mono DTS files — and vice-versa —, but again, AFAIK, there are no free tools (nor commercial ones BTW) capable of the task. Sadly, even
DTS, Inc. themselves have NEVER released a
full-featured (specs-wise) DTS encoder...
