[widgets] Zip vs GZip Tar

I'm sorry if I'm not familiar with all the details of how the widgets spec
is going but the specs encourage comment so I'm commenting :-)

It seems like widgets have 2 uses

#1) As a way to package an HTML5 app that can be downloaded similar to a
native
    executable

#2) As a way to package an HTML5 app that can be embedded in a page but
easily
    distributed as a single file (ie, do what Flash / Silverlight / Unity3D
    currently do except based in HTML5 / EMCAScript)

Use #2 would benefit tremendously if like Flash / Sliverlight / Unity3D the
application could start as soon as it has enough info to start as supposed
to
having to wait for the entire package to download.

To accomplish that goal requires using a format that can be streamed.
Zip is not such a format. Zip files store their table of contents at the end
of
the file. They can have multiple table of contents but only the last one
found is valid. That means the entire file has to be downloaded before a UA
can
correctly figure out what's in the file.

Has there been any consideration of switching the spec to a stream-able
format
like gzipped tar files?  It seems like a shame to miss this use case.