Zip support is unlikely (zip support itself is already in, modo.res is just a renamed zip file). I am facing big problems with my current implementation of the browser and playback module for zip support in the case it contains multiple playable files.
I added an test option to disable the files check. Its works good and browsing is very fast, but you are then responsible to feed valid files into modo. A side effect is that it shows every file and you loose oversight. I can not filter for file extensions only, because many old amiga tracker files does not have any. But if you only navigate in a well sorted music archive this shouldn't be a problem I think, compared to the speed gain.