An option should be added to the GC.dump_heap command, to write the hprof file in gzipped format.
This usually saves a lot of space (about factor 3 in our tests).
Heap hero already let's you upload gzipped hprof files. And the Eclipse Memory Analyzer (MAT) has recently got this feature (see https://bugs.eclipse.org/bugs/show_bug.cgi?id=438844), which should be in the next official release.
Since the deflate algorithm used in the gzip format is not very fast, the compression should be done in parallel as far as possible.