If I'm going to do it I'd like to make most of the necessary GM sounds so it works for everybody .. don't have a large enough sampler.. was hoping maybe PGMusic would like the idea and build it..

A sampler triggers a wav file for a duration of time at a certain pitch, that's all it does really (along with incorporating velocity, etc and other basic midi info). So you could trigger a loop as easily as anything else, I would presume. Barring any bitrate issues (etc.) that would hold true for any wav file.
In my head I envision realtracks just triggering a section of a wav file like a sampler, but with more intelligence. Using the existing stretch/pitch engine to add a sample player would be huge IMO, especially with the mentioned realdrum samples...

Make your sound your own!
.. I do not work here, but the benefits are still awesome